Resurrecting this old nugget as I'm trying to do exactly this.
I followed all the instructions and have checked I have the wiring right. I couldn't find the original RS relay, but found the one pictured below which I believe does the same thing?? Anyway, long story short nothing is happening when I move between games on the Arcade SD. I've double checked that the trigger wire id coming from the J pin on the harness (Had to add a wire).
Kinda stumped. Any ideas?