I changed the floor out in an 85 lunker 2 years ago. I didn't want to remove the live well or the side compartments that hold the flotation foam either. Instead I removed the foam from inside the compartments but cutting and breaking it out. It was the slowest part of the hole process. I then removed all of the screws from the flooring and cut it from front to back in the area under the compartements and remove the old floor. When I put it back in I didn't want to mess with having to go under the compartments again so I put in sections of 1/2 inch white pvc with the carpet attached under the compartments. The length of the pvc pieces was 4 ft, and they ended up about 18 inches wide. I ran them out to the center of the boat to the second stringer, they run front to back in that area, and screwed them down. That left me with a section in the center of the boat that started at the back and was 8 feet long. I used an 8 foot long sheet of plywood cut to about 2 feet in width for that section. The rest of the floor to the front was replaced in the same size and shape as I pulled out. It worked out real well and I haven't had any problems. For the flotation in the side compartments, I used 1" bead board from a building material supplier. I got that idea from two companies that replace flooring. They said they didn't want to foam it and that the bead board would be a better deal because I can easily remove it and put it back in if I need to in the future. They use foam because it is fast. Cutting the bead board does take time.