Coating my Class-C roof

If you're going to recoat a fiberglass roof, why wouldn't you recoat the fiberglass side walls????? Just clean the roof and reseal all the penetrations with the sealant that Winnebago calls out. You can look up the sealants that Winne uses in the info on their website. IIRC, they used two or three different sealants on the roof penetrations. They used a flowable silicone around skylights and they likely used a urethane in some other areas. If the silicone around the skylights is unmolested, leave it at is because it's extremely difficult to get anything to stick where silicone has been previously used. You can find the correct sealant information at http://www.winnebagoind.com/diagram/Sealant.htm