I'd also want to make sure there is sufficient metal on the top side. GW uses fairly large mounting plates ((3) 6"X8") that are welded to the rocket launcher. This ensures any stress is spread out across that area on the top. Hopefully there is some sort of plate on the topside of the hard top. Bolts alone would not be enough IMHO. Plates would be better and plates welded to the rocket launcher would be best.