But I have some questions... why? Are you going to be adding more controls or just looking for more elbow room?
Some sort of change is necessitated by the new trackball. I'm using a PC trackball in there now, which has a tiny footprint (about 3" x 4"). I've bought a Happ's trackball that has a 6.5" by 6.5" footprint, and it will physically not fit into the same space. In addition, thye most popular trackball games at my house are Shuffleshot, World Class Bowling, and Golden Tee PC, and we get our fair share of fingers banged into the glass, so if I have to extend my CP anyway, I'd like to give it enough room for follow-through (my testing seems to indicate that I really need a minimum of 8" between the center of the ball and the glass).
So I have three solutions: extend the panel, build the panel like a drawer and pull it out farther for trackball games, or scrap the cabinet and build one more suited to a larger control panel.
As it is, I'm using the Happ trackball externally for now as a handheld controller; after using it, I just can't go back to the Logitech ball in the control panel... I need to get it solidly mounted so I can play Marble Madness!
As far as extra controls, they are not the reason for doing this, but if I find the room on the enlarged panel I may add a 4-way stick and/or a hard drive spinner, but that's just frosting...
--Chris