I know this is an old thread, but I have a keel version with the exact same problems. I am not sure I can physically get inside the hull to do the repairs though
The floor is rock solid. After I put the boat back on the trailer, the major flexing around where the boat sits on the trailer bunks was eliminated. Overall I can say this job outcome was very satisfactory. The floor is stronger than it ever was. Every piece of wood going in there was coated with west system epoxy on top of already being marine grade plywood. I expect the fiberglass to rot before this wood does. Haha.