Quote Originally Posted by PJ-27 View Post
@Jamie, don't the gearboxes just spin in the mounts? I imagine cutting a square would allow too much play.
Only if you cut it too big, and even then, the gearboxes will only rotate by a couple of degrees. Here's what you're effectively doing:

drill.png

So instead of cutting it to perfectly mate with the drill, the four corners (blue bits) are now just gaps. The properties of a rectanlge mean that it's not possible for any rotation to occur because the top and bottom are restrained in a gap of 25mm and the left and right sides are restrained in a 30mm gap