Oh yeah, I wanted to add that there is a ton of space inside this control panel. You could practically park a truck in there. Even more practically, I could easily fit the computer (either the Raspberry Pi or the Mac Mini) in there).
So, I think we'll probably do exactly that, with the computer firmly affixed to the bottom of the CP, and ports or cables on the back for power, audio, and video connections. This way we'll be able to bring in just the CP and plug it into our TV or a monitor and speakers while testing and debugging the software. This is a big win, because the cabinet itself is in the garage, and I live in Arizona, where the garage is much too hot to actually go into for more than a few seconds.
But yes, I do realize the danger here... that we'll get the CP playable on its own, and never finish the cab. But we have two things helping to guard against that. First, we've already promised the relatives that we'll have the cab complete and ready to play when they come visit for Thanksgiving. Second, I'm documenting our project here in this forum. So if I don't finish it by November, I expect loud and merciless public mockery!