Sorry if I didnt word the question very well. I have the tops apart for paint and I did rust-proof the back of the metal (factory doesnt do a very good job). On my last Z I used urethane window sealer, which was perfect-no leaks- but probably wouldnt come apart without breaking the tops. I'm thinking about using Strip Caulk, but maybe others have experience with sealer that worked well/ not so well (eg Butyl, silicone) ?