I had no problems with my wiring or feeding. The box mag->proprietary electrical switch interface needed a little jiggling (i.e. first time it didn't fire, removed, reinserted, it fired).
ROF was good despite the battery dying out in mid-game (I used a below-spec battery because my designated battery hadn't arrived yet). Feeds like a dream.
All your questions can be answered on Arny's. There's a 54-page thread there.
Contras A-06: F**k it, we'll do it live.