Don't even bother reading this.

Log Goal: make the ultimate movable base of comfort, for my movable buttons.

SketchUp measurements: Minimum 5mm material support around cup for ball. Minimum 2mm adhesive fabric hinge spacing. Ball 38mm. Minimum 40mm cup hole. Tapered cuts are for vertical movement.
1st row, Top
Middle: 50x50x2mm
Left/Right: 50x50 right angle then tapered 15deg bottom
2nd row, Cup row
Middle: 50x50x2mm
Left/Right: 50x50 then tapered 15deg top and15deg bottom
3rd row, structure row
Middle: 50x50x2mm
Left/Right: 50x50 reduced to half width at bottom then tapered 15deg
4th row, bottom row
Middle: 50x50x2mm
Left/Right: 50x25 reduced to 0 at bottom then tapered 15deg
Dimensions laid out flat:
154mmx206mm (6.06”x8.11”)
Argg! Too big!
Dimensions at smallest footprint
125x181 = 4.9”x7.1”

Fail!

I could fit enough tactile buttons for 114-key keyboard and have room leftover for the scroll wheel and some snacks.
I am going to concentrate on the much better movable button idea, which is more realistic, then work a cool design around that.

The good news is I came up with an idea to save space. Instead of a separate scroll wheel, program the Teensy to read the ball movement, and use one of the buttons as “temopoary scroll wheel”. Maybe with options for left click to exit, click again to exit, and automatic timeout.