I use PL brand polyurethane roof sealer on body seams. You can buy it at home repar type stores. It works great. It works as a structural agent too as when hard it becomes a very tough, tenacious rubber. You can't tell it from the urethane that is used to glue windshields in with. But I wouldn't recommend it for that! Lots cheaper than seam sealer too. It also holds paint pretty well. Tim Spry Rochester MI