Just a shout out " bolt vs weld" ....our first 5th wheel trailer was a new 1984 26' Aljo by Skyline. It came with the usual thin 4"X 4" tube rear bumper/slinky carrier. Back then bolt on receiver kits were common. I had a weld/fab shop cut the thin tube off and fab/weld back with a 1/4" wall 4"X 4" square tube. I then bolted my receiver to the heavy bumper.
The fab shop fabricated/welded receiver hitches on mostly commercial trucks/trailers. I mentioned bolting my receiver to the new tube but they didn't recommend any bolt on hitch on the back of especially trailer. They saw lots of loose nuts and bolts and elongated holes. Well I was back 6 months later with a loose receiver....for them to weld it in place.
I towed doubles with a 3500 lb bazz boat behind the Aljo 5th wheel trailer.
My next two 5th wheel rv trailer had custom fabed receivers welded in with more cross members and bracing for heavier trailers so I could tow doubles with my 7k flatbed/cargo trailers.