Oh good god! I too was going to go with the massive button overload on my panel until I made mention of it here on these boards. Instead, I settled on a panel that I enjoy, and with the use of a shift key, has all the buttons I need.
I have two 8-way Happs Competition Joysticks, 7 buttons for each stick, a 3" Happs Trackball with a left mouse button and a right mouse button directly above it. There's a 4-way Ms. Pac-Man style joystick that has two buttons to the right, but the center of those two buttons is spaced right above the left trackball button. In a complete mirror image, the spinner is on the right with two buttons centered over the right trackball button. There are also the P1 and P2 start buttons.
I plan on putting a shift key on the right back side of the control panel and use that to access the tab menu, exit, pause, etc. when pressed in conjunction with the other buttons on my panel. Sure I have a lot of buttons on there (23 by my count), but with the use of that shift button on the side I can have all the buttons I need right there.