Hi,
I only used a IPAC2 in my 3 sided cabinet

I wired it up as normal but I put a 3way toggle switch on the earths running to the control panels.
This meant that when playing a vertical game only the 2 end panels would work so nobody could muck with the horizontal panel.
Flick the switch the other way and the horizontal panel comes to life. In the centre of the switch all the panel work for 4 player games like Gaunlet, but you have to be a good gamer to play on the vertical panels. I eventually had a brainwave

and just reconfigured the joysticks in MAME so the directions turned 90 degrees accordingly. This meant you could sit more around with the horizontal panels and get a better look at the screen. WAY COOL!
I would just start off with the frontend on horizontal and run all the games like that for your mates. Once they get the idea then change it or maybe run one game in full screen and show them what panels ot use and then change the game after everyones had a turn.
Have fun!