Update
Well, I took a week off to reflect on my ignorance and to formulate a plan. Since the tub no longer fits the frame, I figure I really only have two good options.
1.) Have metal bent and put together a new tub from scratch. So, while I was cooling off, I made a trip to a local sheet metal fabrication company to get a quote. They suggested bending each side and having them meet in the middle of the floor. This way there would be just one welded seam down the middle of the floor. Then of course the two end caps. The quote for the metal and the bends and cutting the end caps was $520. If I ever build another trailer, I will fabricate the frame from scratch and then go this route for the tub, but for this project, $520 is to much money.
2.) The only other good option I could come up with is to build a sub frame out of 1" x 2" tubing. Basically, a spacer that would fit between the tub and frame. One that is slightly narrower than the frame to fit the new width of the tub. I decided to go this route since the cost for the materials was only $57. The problem of course with this is attaching the sub frame to the frame, and of course raising the tub an inch means that none of the bolt holes will line up and neither will the fender mounts where they attached to the frame. Still, it seemed way easier than starting a tub from scratch, and way cheaper.
On the bottom, the floor was only spot welded every couple of inches, basically to keep the lip from bending open. They weren't really structural type welds, so a couple tore loose when I started beating and bending metal. So, I ground off the undercoating and seam sealer and re-welded the areas that had broken free.
Primed, laid down more seam sealer and repainted.
I made a frame out of 1" x 2" tubing to fit between the tub and frame. The silver lining is that while I am at it, I can add some support for the floor over the large open area above the axle.
The thing I found very interesting is that the sub frame that I made is perfectly square, but it doesn't fit squarely on the frame. In fact, it doesn't fit the frame, much the same way the tub doesn't fit the frame
Now I'm wondering three things
1.) Did the frame somehow move out of square during this process. If so, how?
2.) Is it possible that bolting the tongue arms and lunette receiver back together could tweak the frame? This seems unlikely. But somehow, the frame is no longer completely square.
3.) Maybe these tubs are mated to frames before they are completely welded up and this frame was out of square from the beginning? Seems unlikely too.
Anybody have any thoughts?