We bolted bus seats to the front and rear racks of my friend's polaris quads so they cold carry 7 people (sortof) and we only had two helmets. We were only going about 25 mph, but dear god, 25mph with an ass cheek hanging off the side is scary as hell when the guy driving the other quad is trying to do anything he can to make my driver go off the road into the field. I did manage to fall off at one point but thankfuully I landed in the sand and not on the gravel.
Good times... Man was that ever retarded