I replaced the floor of my bedroom slide with 1 inch thick marine plywood. I used the original floor as a pattern, cut it out and sanded it. Then I put several coats of spar varnish on all surfaces. Then installed the new floor. Preparing the new floor took a few days in order to give the spar varnish time to dry. Installing the floor was a one day project. Much easier than I thought it would be.
This was done in the spring of 2012. I have used the camper many times since then and the floor shows no signs of wear.
I also sealed the bottom corners with eternabond tape and trimmed it so it would not land on the delrim blocks that it slides on.