Here's a good one.
That thread is massive, but a few folks actually performed and documented the fix well (notably SuperTrouper, beginning around page 18).
If you have the rear bumper leak, which is far too common in the age ranges of our trailers, you'll need to drop the belly pan (not as hard as it might seem) and remove the insulation that's under the floor. If yours is like mine, that insulation actually traps the water like a balloon and keeps it under the subfloor - due to the rear bumper leak. I've cut mine away and am letting it dry a few weeks, then reinsulating with some sturdy foam board type insulation. I'll use something to shim it away from the actual subfloor before installing it.
PM me if you need to discuss.