The problem here is that is not the NeoGeoLand popup menu, that is the main menu (I grant you it looks very simular though).
Wouldn't it be possible to use the main menu window in the BIOS? Then, you'd have that stripe where the button icons originally were, for all the info you want to put there. An in case you'll ever support more multicarts, it could also display which one is currently running, the 191, 150, 138, or whatever. This would certainly solve the awkward placing of the PICnMIX text, and you could call it PICKnMIX, because PIC sounds weird to me, like a short "picture", not "pick".