Belly Skin repair
After removing rotted floor sections in my 54 Safari, I have discovered that much of the rot and mouse/critter nests (huge!!) were caused by compromised belly skin areas, areas crudely cut for piping, wiring, etc. This was particularly true behind the wheel wells where tons of road debris, both wet and dry, kicked into area between floor and skin.
I have found fiberglass mat impregnated with resin, usually used for cars and boats, to be any excellent area repair. It is tough and durable and can be built up. I install the matting from inside the trailer. An outside layer can be added, if desired. In addition, it can be shaped to most contours. Make sure attaching points are ground to clean metal.
This method is fast, easy and requires no additional holes to be drilled as in metal repair patches.