Hi,
It's fine to do this to eeproms, (24xxx types only).
you can short them together or to pin 4 (gnd)
Nice game cab btw, I've got one in the garage I'm working on too.
I've got the cab, joysticks and buttons, a nice amp, pc (going to use it for music, mame and other games), but was considering putting an old xbox instead as I got one for a few quid the other day - think it will stay pc tho.
Cheers,
Si