Fixing stripped ECU screw for proper ground???!!!!

One of the screws to my ECU is loose / stripped. Cuda still starts so its not a ground issue yet. Anyway, I can't get my arm in far enough in the wheel well to use a nut to secure it properly. I was thinking a star lock washer on the fender well to ECU then another from the screw to the ECU in order to lock it in place for a proper ground. I really don't want to drill a new hole in the fender or drill a larger hole in the ECU for a larger screw. Fire away with your tips!
Being that I can access behind the cowl on most of my cars, I ran through with a bolt and used a lock washer under the nut.