Specifically, my idea was to use the CNC to cut the part itself out of the polystyrene foam such that I have a positive mould, which I would then coat with a thin layer of epoxy. I then intend to use the Uni-Mould system, treating the epoxy-covered foam as a regular part, to obtain a negative mould. Any suggestions or reasons this would not work? I am especially concerned about the layer of epoxy on the polystyrene foam reacting with the epoxy-based gelcoat and hindering its release.