I am a fan of the classics, so I did not set up my CP for four players or six buttons per player.
I used the extra I-Pac inputs for a row of buttons at the top. most of these buttons are set up to serve a dual purpose using the shift function. I did not want to have to explain (or remember) what that shift player1 button 1 was the tab key.
Across the top I have Pause, Advance, Coin 1/shift, Start 1, Start 2, Coin 2,On Screen Display(~),Config(tab),Enter
The shifted functions are Escape, Reset, shift, Start 1, Start 2, Coin 3, Save, Load, Enter.
Escape and Reset are shifted so that they cannot be hit accidently.