if you used wood it would be MUCH thicker! the sheet metal is only about 1/8" thick.
anyways i have another CP that is made of metal. just get a 1 1/8" bi metal hole drill, it cuts through the metal nicely... even easier if you have access to a drill press. and mounting joysticks are a breeze, no routing, just drill 4 holes to hold the joystick, a 1 1/8" hole in the center and mount!
i am sure if you looked in your yellow pages you could find someone that would sell you a pre cut piece of sheet metal!