Thanks for the info. I didn't actually start routing anything, although I did build a standard Happ template so I can easily route the underside of the CP using a collet.
I would appreciate more pairs of eyes on my new CP layout:

At the top are the four "Coin/Start" button groups. And then, working counter-clockwise from the top left, we have the standard player 3-1-2-4 setup. Four buttons for players 3 & 4; seven for 1 & 2.
I placed the spinner dead center -- the only games I play that use the spinner are Tempest and Arkanoid. The positions seem to give me a nice place for my forearms using the spinner either left or right handed. On either side of the spinner are Player 1, Switch 1 buttons.
To the left of the spinner is a Pac Man 4-way joystick. The Player 1, Switch 1 buttons from the spinner will work nicely for games like Donkey Kong.
To the right of the spinner are two top-button joysticks for Battlezone; but also for games like Robotron.
I placed the trackball in front of the spinner, between players 1 and 2. Doing the "Golden Tee" move at the trackball position didn't ram me into the spinner knob, so I think I'm good there. The buttons for the player 1/2 positions will do the trick for games like Missile Command and Centipede.
At the top center, I plan on placing administrative buttons -- ESC and Pause. And a Keyboard will slide out from the bottom for fiddling.
This isn't going to allow me to play everything, but I think this will work nicely for the sorts of games I play the most. If you see any glaring errors or omissions, please let me know.