PT wood is nasty stuff, wear gloves always, and it is nasty stuff and will give cancer if you live long enough and it will off-gas so you breath the nasty.
I'm not sure "getting back in" is the goal, but fiberglas can be infinitely cut and re-epoxy'd
I missed that you need more bed rail clearance. Lots of post about using plywood to make two X's as both to lay under the camper and increase height and to give you a mobile platform to lower the camper onto for storage or extra stability at the campground. I like to have something under the floor when it is out of the truck as when I rebuilt the bottom I used foamboard, not plywood so it is less rigid already.
My Dodge has high rails so 3/4 plywood and a rubber mat give me enough height, and I always have the bases with me.
