I know your post wasnít directed to me but I might be able to give you a little insight. I found I had a problem with mine when I brought it home, my brother-in-law was following me and he said the bumper was loose. He said it was moving up and down about 4 inches while traveling down the highway, the PO had replaced most of the floor and had not bothered bolting the shell back down to the floor, thus the problem. Another problem was he had severely overloaded the trailer. You can see some of the floor patches in the link below:
I am replacing the floor without removing the shell, Iím going to cut the new floor 88 1/8" then split it in half, the 1/8" is for the saw curf. I have welded in a 2" wide strap the length of the trailer on the centerline for the plywood to rest on, it will also be a platform to bolt to. This is just a poor mans way of doing a complete floor replacement with only one person. See picture in link below:
The strap welded in has added a lot of stability to the frame without adding a lot of weight. Once the plywood is bolted down at the seem I believe it will be as strong as a complete sheet, anyways I'm doing this alone and can't lift the shell. Also in the second picture you can see part of an outrigger I welded in. The one that was there went on a walkabout. Don't know what happened to it.