Hi JaySam.
Your rebuild looks great
I was in the process of doing the same thing as you to the ceiling. I had planned on 3/4x3/4 steel in ceiling. Also I removed floor carpet to lay new floor. But after carpet removal I noticed floor sag at the walls. I noticed that you welded braces to your frame for more floor support , were you able to jack the walls up or ?? Did your floor sag move at all when you jacked up the ceiling ? I really did not want to lose headroom by adding 3/4 plywood to floor, is there anything you wish you would have done differently to stiffen up walls or floor . Any help would be appreciated. I have already spent many hours and dollars on my sunrader since last year and it never seems to end.