It doesn't work well when the 5200 is under a large protected surface, like a beam. Trust me, I've seen an I20 deck broken after a week of trying to remove a beam that was seated with 5200 using every ointment and/or spiritual fix we could dream up.

Don't seat beams with 5200 or 4200. Wax the aluminum beam with mold release and use epoxy or polyester resin infused with a filler. You can dam up the edges with clay or rope-type window caulk putty. Your hull socket will be perfectly fitted to the beam AND you can remove it and reinstall it without messing up the joint or having to deal with un-removable sealants. Besides, why would you fill the joint, that you are trying to firm up, with a flexible compound?

Weren't we talking about rivets though?