Teardrops n Tiny Travel Trailers

I added a spare tire mount and a propane tank mount to the sides of my trailer a few years back. They act as real good parachutes and the first time I towed it I realized it was a bad idea but the van I had at the time could kinda-sorta keep up with it as fast as I was willing to pull the trailer. Van crapped out, new van has a smaller engine. Any source of drag I can possibly get rid of has to go with this new van! I'm going to remove the spare tire mount and the propane tank holder and relocate them but that'll leave a bunch of holes in the side of the camper where the mounting bolts for the brackets used to be.

The camper is 3/4" birch ply (UV finished on the inside so cosmetic repairs/blending is basically impossible) and a very thin aluminum skin outside of that (pretty typical construction). I'm not concerned with how it looks, I just want whatever patch I do to be durable and absolutely watertight. Best thought I've had so far is to just take a little piece of aluminum (I don't have any more that matches) and glue it down with something like 3M 5200 or Sikaflex. Do you think I can get away with just an adhesive bond like that for both mechanical fastening and waterproofing? Do you think I need to use something thinner than the really thin aluminum flashing type metal I can get around here?

Any general thoughts and advice?

I would fill the bolt holes with plugs, either cut or from pieces of dowels, glued in place with waterproof glue. They would be finished flush with the side surface. Over that the aluminum idea you have would work fine since there would be no stress on the patches. Adhesive would be fine. An alternative for the aluminum would be self sticking foil tape. Should make a watertight patch over those plugged bolt holes. Good luck with your project.