Teardrops n Tiny Travel Trailers

I created a poor man's illustration below. Yellow box represents the camper body, black lines represent the roof sheet, blue lines represent the side walls. I want to bend the roof sheet with small edges on all four sides, the edge size can be 1/4" or whatever the size that can be covered under the edge trim, then tug the side wall sheet under the roof edge. I hope the overlap edge can help preventing water leak. Is this the right approach to do it?
Thanks!

In my opinion your making it more complicated than it needs to be. Just run your sheets to the edge. Use a good quality polyurethane sealant under the trim when screwed down. I drilled all my trim and sheeting(not into the wood) dry. Then removed it, cleaned up the shavings, deburred the holes. Then assembled it with sealant, and screwed it down. Sealant oozing everywhere! That's where tape and prep come in! Sealant socks for cleanup, but won't leak!

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Agree with the above. Cut aluminum sheets so they go to the edge, and put sealant under them. Then screw down an aluminum L-shaped edge trim over some butyl tape and it will never leak. My roof edge moldings have a slot for a vinyl strip to hide the screws.

Thank you lfhoward and dmdc411 for your response!

I also can't figure out how to handle the aluminum at the bottom of the ply as shown in the picture. I see 2 challenges:
1. I have fender tubes and other metal mesh welded around the frame. For the sections that aluminum cannot be wrapped around the bottom of the frame, I can only place some sealant on the bottom edge of the aluminum. Any suggestions what's the best way to do that? I suspect I'll have to periodically reapply the sealant. Is this a design flaw I made?

2. I also realized that my 3/4 plywood is tightly squeezed between the fender and floor side. Any concerns with the fender rubbing the 040 aluminum and damage that? Do I have any remedy at this point? I tried to trim off the floor edge slightly, it was quite a struggle due to the tight space.
Any help is greatly appreciated. Thanks!

I can tell you what I did at the bottom of the trailer body where it met the frame. First, I used PL Premium to caulk the gap (small as it was) where the end grain of the plywood met metal. Then, when skinning with aluminum, I put a generous bead of Sikaflex 221 between the aluminum and plywood at the edges. I sealed the aluminum to painted steel junction with another external bead of Sikaflex 221 that I smoothed out. The external Sikaflex needs to be redone to reseal this bottom seam about every 2-3 years, but I do keep my trailer outdoors. Pics from my last re-seal in 2020:





And here is the stuff: