Hi Scottie.
This isn't my invention, but I can't remember which website I found the thing on. I'll keep looking, but this is mostly a rough sketch of what they had.
This view is from the underside of the Control Panel.
The control panel has the green blocks attached to it at the Xs. These blocks support the inner circle and keep it from falling thru. You'd probably want to make these pretty sturdy.
The inner circle has the red blocks attached to it at the Xs. These keep the inner circle and joystick from being lifted up and out of the panel. They also act as stops, limiting how far you can turn the joystick.
The other guy's drawing had specific angles for the blocks, to make it perfectly rotate 45 degrees before stopping. The spring pin could be sprung out from the center disk, lifting up to fit into a turning groove, and dropping back down to lock the new position in place...