I use all 8, but only 7 to play. the P1 S8 is a dedicated Pause button and P2 S8 is my middle button in a 3 button layout for my mouse (missile commnad layout).
My buttons are laid out as such:
123 (All Blue)
7456 (Neo Geo Colors)
You can use a Controller.ini file to make the Neo Geo buttons take over when playing NG games. then it will look like this
XXX (not used durning play)
1234 (In order of neo geo colors too!)
You have to use the switch -crtl when using it, but i haven't figured out how you would do this from a FE, say MameWah. Does anyone know this one?