jayspi, how good of a DIYer are you? I'd personally pull the slide box out of the camper (not as scary as it sounds) and replace the bottom where I could work easily to keep everything square and true. I'd use marine-grade plywood as well and do some flashing work with aluminum to keep water out. Your dealer is talking about the same material used for spray-in pickup bedliners. They are using it now in lieu of the fabric and tape, especially on slide-out boxes. I would definitely have this done if taking the box out or repairing in-place. You just need to find an applicator that can do it (not all the pickup sprayers are certified to also install in other applications - see Rhino and Line-X websites).
