I would, but I need to load +5v from my cabinet's psu, not from the PC psu. My cab's PSU goes into overload mode w/ out a board (ALL my wiring is jacked through the PSU, so I can't remove it). So I'm going to just load my PSU w/ a dummy jamma board, thus the 5v.
I just read this on Bob Robert's site, which is essentially the same thing you said:
<<The PCBs ground traces are all linked together on both sides of the board, so any place that is designated as ground on the PCB, is just that, logic ground, and unites all logic ground into one common termination back to the supply grounding point at your source of DC power.>>
So I'm assuming by splitting a ground, there won't be any problems since they are all linked together.