No I only used zip ties initially. The whole process was to get a rubber plug with a hole in it for behind the plate and behind the grill. Then I put a big bolt with a washer through the plate and the two holes (the bolt obviously has to be small enough to pass through the grill) and then I secured it to the other side with a nut. Haven't had any problems since.
So the bolts don't scratch the grill at all? Doesn't the plate move up and down and side to side on your jeep?