Our 5th wheel is I-beam construction so I dont see an issue with that part.
The only thing in the rear of our trailer is the kids bunk house which is two slide outs.
With a outside kitchen a small one so there isn't much weight there to begin with.
I don't plan on it being a permanent part of it unless I really had to make it a fixed structure back there.
We would use it on long trips but it's for when we travel to our property in the middle of no where and want to stay for a week or so. There is no any type of hook ups out there.
I'm thinking of I remove the rear bumper and suck the hitch and frame up as close as I can to the body of the camper to eliminate as much over hang as I can and stress on the welds and bolts.
I don't plan keeping it loaded with fuel all the time either.