I made a sample layup of the method previously described. The basic setup before applying syntactic foam. 1/8" deep roller for applying the foam. The wing skin with foam. I have not yet glassed the inside. The foam was rolled on under a layer of polyethelene plastic on a flat surface. The mix was 1 part epoxie resin, 2 parts microspheres and 4 parts expanded polystyrene micro-beads.