... with Mixed_Curve in CurvesWB you get a fair transition.

... a more ergonomic knob variant in PartWB, combined with Fusion:

... put your letter_X on XY-plane => remove filled property.
Scale it only in X-direction by using Link tool or anything else.
Make 2D-Offset "filled". Extrude this face.

... and use Polar_Array instead of a complicated Sketch:

... scaling with Link tool:

... und hier mein "Morgen-Denksport" => 13 min länger:

... last version:

... core finger model by BSpline cross sections.
Sketch_On_Surface with additional Sketches.

... one of the possible tools is Blend_Surface in CurvesWB:
(FC-file 2,7Mb => too big and complicated for posting)

... from Heda's file redrawn just for fun.
(A little bit bigger !! Because I had to do with the CRV-vehicle Bodyflaps some 25 years ago).
https://en.wikipedia.org/wiki/Crew_Return_Vehicle