Got the joystick mounted. Seems solid but what a pain in the neck! I ordered the
joystick mounting kit from groovygamegear but the screws that came with it were 1/2" which was too long (the CP is only 1/2" thick). So I had to go to Home Depot to find some 1/4" screws with the same threading. I thought about using washers but I was concerned about the two screws near the top of the panel sticking up too high to not allow the CP to sit flush.
Anyway, I got the plate lined up from underneath and marked the center point for the holes for the t-nuts.
I used my awl to punch a hole in the center where the forstner bit will start drilling and then used painter's tape to try and minimize tear out. I used a 5/16" bit to drill down - I had to go super slow and check the depth every mm or so. I wanted the deepest hole possible without going through (or warping) the other side.
Then I used the Allen wrench that came with the joystick mounting kit to screw in the t-nuts... this was also difficult because I had to keep everything centered and because my panel was so thin and made of MDF, it wanted to tear out rather than go into the hole.
It worked in the end and the joystick is very secure and you can't see anything on the top pf the panel. I'm glad I went this route instead of drilling through the panel (which I was prepared to do if this didn't work).
Of course, I forgot to take pics of the joystick installed but I'll do that tonight. Next up - installing magnets to keep the CP in place!