I also contacted them regarding waterproofing and was told that the gripset RD . The reason for this is that the caravan will not be in water or out in the weather for prolonged periods. The gripset RD also has UV and fungi/algae retardant in it. It is also very flexible and in a range of tinted colours. I still had to prime the van and apply heaps of coats. My Castle Caravan is finished in acrylic paint as it offers more protection than oil-based. My Convair is oil-based and will stay that way as I have no control over that. As for a silver in water based paint Maybe someone else knows