I did some work around the floor, recently and replaced the frames on the two side windows
. I found tears in the GRP (GlassReinforcedPlastic - ie. fiberglass) at the front of both fender wells. I repaired that with epoxy GRP after cutting out the lower parts or the closet and sink cabinet for access. Another member here had the same problems. Patched the furniture back together after.
In any case. What I want to say is that it looks to me like _everything_ in these trailers is structural! The GRP around the side windows
is less than 1/8" and I found several places around around the windows
where the GRP layup was resin-starved. Ie. not enough resin was used and the glass strands were dried and not melded together well. I have a 1977 and these particular problems _may_ be particular to that year. But overall, the trailer is NOT "overbuilt" and all the funiture _and_ the window frames appears to be structural. The floor certainly is. In mine the top shelf of the closet is "tabbed" to the exterior shell - meaning that closet is holding up that wall. I'm certain the cabinet carcass for the refrigerator
is doing similar duty on that side. The window frames of the side windows are what holds the rear locker up.
What I am saying is: Make great effort to not weaken _anything_ in the trailer. When there's access and time/resource it looks well worth thoughtfully strengthening any areas you work on.
The key, though, is "thoughtfully". If you don't understand "stress risers" and "hard points" then it would be worth talking with an experienced boat repair person or studying up on GRP work. It's not rocket science but there is some concepts in GRP work that matter.The best info I know for this stuff is books on old GRP boat repair. These are easy to come by. GRP is usually messy, smelly chemical-rich work. Epoxy is by far the best resin to use when attaching repairs or new glass to old existing glass. Epoxy is not nice stuff and workers definitely should use gloves and avoid breathing the fumes. It's a cumulative problem, so low level exposure over a period of time can tip into a full blown allergic reaction at some point. That's why we use protection from the get-go, even though the process can seem "no big deal" for several years.