Thank you , I bought some 12 Ga metal and I'm fabricating a few of them, however having your design will help verify my measurements!!!!I made one but as others have mentioned it will not support the switch's weight.
I have most of the weight sitting on a couple ears mounted under my desk from a print on thingiverse.
Also the holes are slightly small for the screws into the switch.
The screws will tap a thread in the print if you don't enlarge them.