I am a very novice CAD user, so the STL has a lot of flaws - not smooth edges, lacking symmetry, etc.
I really wanted to mount a trackball to my ZSA Moonlander, particularly for my right thumb. I took a BTU mod of the top part of the Ploopy Nano (BTUs make the trackball roll soo smooth), and attached the remix of a previously made thumb cluster blank.
I angled the top so that 1) it was a little closer to where my thumb naturally sits and 2) so that the nano sensor was oriented a horizontal/vertical axis (so that I didn't have to scroll diagonally with the trackball to go up/down/right/left).
If using this attachment, I recommend reflashing the ploopy nano sensor with a keymap that has #define POINTING_DEVICE_ROTATION_270
removed from the config.h file; the default configuration, with the rotation I introduced, makes it sideways.
Note to improve the stability of the mount on the ML, I used heat-set inserts. That is why I changed the dimensions of the holes to be beyond the M3 screw diameter.
The author remixed this model.