I bought some Dapt(cheap stuff-next time the industrial)but it filled my quarter panels below the rear armrest nicely. Took two days to dry completely though...must have been the depth/density. I was pleased to find out that it will stand up to fibreglass resin. Construction foam insulation panels dont and you have to buy epoxy based resins which are much more expensive. I think once I am sure it is completly dry I will be coating the Dapt with a 'glass layer for strength-the Dapt is compressible and needs some help.