diff --git a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.iup_optimize.ttf b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.iup_optimize.ttf
index cf410fa11..60366def8 100644
Binary files a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.iup_optimize.ttf and b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.ttf b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.ttf
index 1eaf131d6..5772b362d 100644
Binary files a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.ttf and b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=200-300,opsz=14.ttf differ
diff --git a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.iup_optimize.ttf b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.iup_optimize.ttf
index 391e939e5..557797ed4 100644
Binary files a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.iup_optimize.ttf and b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.ttf b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.ttf
index fd8ce121e..ec326133e 100644
Binary files a/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.ttf and b/test/subset/data/expected/empty_region_vardata/RobotoFlex-Variable.ABC.default.retain-all-codepoint.wght=400,wdth=100,opsz=14.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf
index b6c373dd2..5d138ef29 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf
index 97cc1b2ab..9f2e4a8ef 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf
index e60233179..2447337a4 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.ttf
index e60233179..2447337a4 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.ABC.default.retain-all-codepoint.wght=300-600,wdth=85.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf
index 15c3ddf1c..d659d83d1 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf
index 0c926c802..8bfaadef0 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=200-300-500,wdth=80-90.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf
index 2c3bc8e4e..10ca9fbbf 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.ttf b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.ttf
index 964c46d5e..e96c24009 100644
Binary files a/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.ttf and b/test/subset/data/expected/glyf_partial_instancing/Roboto-Variable.composite.default.retain-all-codepoint.wght=300-600,wdth=85.ttf differ
diff --git a/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.iup_optimize.ttf b/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.iup_optimize.ttf
index 57b33d128..757b2ddf2 100644
Binary files a/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.iup_optimize.ttf and b/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.ttf b/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.ttf
index 2136b9d53..80f18f950 100644
Binary files a/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.ttf and b/test/subset/data/expected/mvar_partial_instance/NotoSans-VF.abc.default.retain-all-codepoint.wght=200-600,wdth=80-90,CTGR=20-60.ttf differ
diff --git a/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.iup_optimize.ttf b/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.iup_optimize.ttf
index 5311eb0eb..1bf7b04b7 100644
Binary files a/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.iup_optimize.ttf and b/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.ttf b/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.ttf
index 5311eb0eb..1bf7b04b7 100644
Binary files a/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.ttf and b/test/subset/data/expected/sync_vmetrics/playwrite_mm.subset.default.retain-all-codepoint.SPED=25,YEXT=520,wght=100-400,slnt=18.ttf differ
diff --git a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.iup_optimize.ttf b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.iup_optimize.ttf
index 3f86e2cf6..46885af68 100644
Binary files a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.iup_optimize.ttf and b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.ttf b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.ttf
index c920c008e..22ea1db7b 100644
Binary files a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.ttf and b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=300-600.ttf differ
diff --git a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.iup_optimize.ttf b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.iup_optimize.ttf
index cdb7567fb..f9435b588 100644
Binary files a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.iup_optimize.ttf and b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.iup_optimize.ttf differ
diff --git a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.ttf b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.ttf
index 7747dd108..278fa73c4 100644
Binary files a/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.ttf and b/test/subset/data/expected/update_def_wght/SourceSerifVariable-Roman.default.retain-all-codepoint.wght=500-800.ttf differ
diff --git a/test/subset/data/fonts/RobotoFlex-Variable.ABC.ttf b/test/subset/data/fonts/RobotoFlex-Variable.ABC.ttf
index 0ca6605d3..d8571ad2f 100644
Binary files a/test/subset/data/fonts/RobotoFlex-Variable.ABC.ttf and b/test/subset/data/fonts/RobotoFlex-Variable.ABC.ttf differ
diff --git a/test/subset/data/tests/empty_region_vardata.tests b/test/subset/data/tests/empty_region_vardata.tests
index f5299954b..a4368d582 100644
--- a/test/subset/data/tests/empty_region_vardata.tests
+++ b/test/subset/data/tests/empty_region_vardata.tests
@@ -14,3 +14,7 @@ wght=200:300,opsz=14
 IUP_OPTIONS:
 Yes
 No
+
+OPTIONS:
+no_fonttools
+# TODO: re-enable fonttools once rounding issues are fixed (https://github.com/harfbuzz/harfbuzz/issues/4642)
diff --git a/test/subset/data/tests/glyf_partial_instancing.tests b/test/subset/data/tests/glyf_partial_instancing.tests
index ebb4566f1..faea3168d 100644
--- a/test/subset/data/tests/glyf_partial_instancing.tests
+++ b/test/subset/data/tests/glyf_partial_instancing.tests
@@ -15,3 +15,7 @@ wght=200:300:500,wdth=80:90
 IUP_OPTIONS:
 Yes
 No
+
+OPTIONS:
+no_fonttools
+# TODO: re-enable fonttools once rounding issues are fixed (https://github.com/harfbuzz/harfbuzz/issues/4642)
diff --git a/test/subset/data/tests/mvar_partial_instance.tests b/test/subset/data/tests/mvar_partial_instance.tests
index 692d78a49..55ef2a2d2 100644
--- a/test/subset/data/tests/mvar_partial_instance.tests
+++ b/test/subset/data/tests/mvar_partial_instance.tests
@@ -15,3 +15,7 @@ wght=200:600,wdth=80:90,CTGR=20:60
 IUP_OPTIONS:
 Yes
 No
+
+OPTIONS:
+no_fonttools
+# TODO: re-enable fonttools once rounding issues are fixed (https://github.com/harfbuzz/harfbuzz/issues/4642)
diff --git a/test/subset/data/tests/update_def_wght.tests b/test/subset/data/tests/update_def_wght.tests
index 13a0e20b9..72882a0d6 100644
--- a/test/subset/data/tests/update_def_wght.tests
+++ b/test/subset/data/tests/update_def_wght.tests
@@ -14,3 +14,7 @@ wght=500:800
 IUP_OPTIONS:
 Yes
 No
+
+OPTIONS:
+no_fonttools
+# TODO: re-enable fonttools once rounding issues are fixed (https://github.com/harfbuzz/harfbuzz/issues/4642)