I'm thinking of re-sealing my roof but not sure what I should use. I know some had Aluminum, some rubber and some fiberglass. Mine's a 2001 24TD. It has been sealed before I bought it so I can't see the texture of the roof. Does anyone know what it's made out of? It may not matter since it already has been sealed before. Can I seal over the previous sealant? It appears to be a rubberized roof sealant and it is starting to dry out and crack. Thanks