Whew. Silver does Class A rebuiilds. I suspect that you are interested in redneck engineering.
Check first to make sure that the floor in the overhang is an integral part of the larger tub. In the Avion it is not. It is attached to the frame and the 8 foot section of floor, but that is the reason that it frequently fails.
So the fix is relatively straightforward. (1) Drop the camper onto blocks to support the floor. (2) Find a way to support the upper part of the affected area - and there's lots of ideas of how to do that depending on the configuration. (3) Tear out the rotten section. (4) Replace section.
You are getting into plumbing and holding tanks and toilets. But they come out and go in like anything else.
Can be done on a budget. Best of luck.
