Recently decided to take the bedliner out for the first time in 15 years, and use Duraliner roll on. I knew I had some rust from working on the EVAP system. My plan was to use existing good part of the bed to make a mold. I taped down some aluminum foil (next time I would find the heaviest foil I could) and applied several layers of fiberglass, cut the excess off and had my panel. Epoxied it in and fiberglassed over that and rolled on the liner.