There's nothing fancy to see here. The only real problems I had to deal with were making sure the control panel did not move at all during gameplay and making sure the control panel was removeable at any time for maintenance or something. My first solution worked perfectly so it turned out to be pretty easy.
I bought some industrial strength velcro from Home depot and put two strips on the lip of the monitor panel that I had previously routed and the matching strips on the top of the underside of the control panel. Once I put the control panel in place it was a very tight fit. The velcro held up nicely and nothing was moving even when I pulled quite hard on the joystick.
The only other issue was holding the bottom portion of the control panel in place. Since there were some strips of wood on either side from when I first assembled the cabinet, I just used some 3" clamps to hold the bottom of the control panel in place. Easy!
Here are the results - it's looking pretty sweet right now.Next up - installing the bezel around the monitor.