Tubs and Toilets

[68Glbtrotter]

I am in the process of repairing a portion of the floor in my 68 Globetrotter. Since water and battery acid have eaten through the floor and possibly the B/W tank, I am having to dig to verify. The skirt around the bathroom is also destroyed at the bottom but may be reusable with some type of molding to cover up bottom.
I first removed the toilet, a Mansfield Model 910 Serial# 903277. Boy was I lucky on this one. It had four screws. All four screws broke loose as I was taking off the nuts but for whatever reason they did not turn (as long as you kept upward pressure on the tank). Again I think I was very lucky cause it was bad enough getting your face down that close to someone else's toilet to get to rear nuts much less trying to keep screw still while turning nuts.
The toilet came off with ease and I have the wax ring on my floor. Somewhere I saw a thread that said there was no wax unless PO did it. Well I guess he did.
Next I moved to the tub. Rivets everywhere and I had trouble finding and getting to some of them. So now I'm at the drain of tub, it will not budge, thanks to you guys, I go get my heat gun, heat it, use regular pliers that fit down into the drain, turned counterclockwise and wala, tub is free. Pizza time, we take the rest of the stuff out tomorrow.
As you can see I have cut out the rotted floor. Any suggestions on how to repair just this portion of rear floor would be appreciated. Even though most of my trailer will be gutted, the floor is in good enough shape that I’m going to try not to replace it all.
Dan

[RestorinanAS]

I can tell you what I did to offer support when I replaced our bathroom floor-not that it would be considered the right way. I never consulted anyone as i probably shoud have. We have a 1964 Soveriegn which I believe is supposed to 31 feet. After cutting out and removing the section of floor, I installed pressure treated 2x4s longitudinally between the steel cross members. The forward one was slotted so that one was easy. The furthest rear beam I drilled through for lag screws. I used wedges between the 2x4's and the new floor and it's tight and level. It worked out very well for me. We don't move our trailer much though which should probably be a consideration. It's only moved about 1500 feet in the last 25 years! Good luck!