I made one of the original Nintendo Switch Joystick Extender Mod 1.4 (WIP) and two of a slight variant I created in advance of even doing the original due to the feedback in the comments of the original. My slight variation was to just cut off one of the legs, and that part works great. It slides on and off the thumb stick quite easily and is firm when in use.
I also embeded the inlaid word "Switch" on the bottom. I'm not really sure why I did that - it's pointless.
I only messed with the concave option, but I found that applying a "dollup" of hot glut to the center of the concave area allowed a texture that was much more pleasant to use.