Correct, but I have a0, a1 (left thumb) a2, a3 (right thumb) a4, a5 should be the dpad or hat. I Did try setting the hat as per this config: https://github.com/ssilverm/PiMAME/blob/master/.gngeo/gngeorc
Still no dice.
I think I might just get rid or GnGeo and use lib-fba