Don't do this
a couple of thoughts, after replacing my floor, 3/4 of the whole thing from front to just before the bath
-take measurements at the floor to make sure the shell goes back in the same shape. Sounds dumb, but the shell can flex, and, well, it happens.
-I used marine ply, nominal 3/4" thick. I sealed it afterward with a two part expoxy sealant because I was still having problems with leaks, and the new floor was getting wet.
-since the floor is integral to the structure, that is, securing the shell of the thing to the frame, I would suggest replacing more rather then less. Sounds ugly, but my experience was that the body flexes and rivets pop if the floor isn't stiff enough.
Advantech sounds cool, impregnated with Phenolic resins... I always specify plywood rather then OSB at the recommendation of two engineers that I use, because OSB doesn't tolerate water as well as ply.
Wherever you go, there you are