I have been playing around with the geodesic foam and resin material from Bragdon Ent. and I am very impressed with how easy it is to use.This mold is my first try and It came out very nicely. The casting is about 12"x8" and weights only about 3oz. Bragdon has a set of earth color paint that I have but I used chalk to color this casting and I like the results. I think there is little cost difference between this and box store foam because a little resin goes a long way. (your mileage may vary). A big plus to this is very little cleanup.
Carl, I really like the look and would love to see some of this process. Have you build up any sections with several molds or castings? Any other ideas would be much appreciated, Pat