I've literally just tried my first casting attempt with a corian mold minutes ago funny enough, the finish detail was excellent, no sanding just some wax release spray. Unfortunately was not enough to get the fiddly little parts to release and ended up smashing the corian to get them out. Maybe casting flexible PU in a solid mold was a little ambitious to ever believe i could reuse the mold but the parts came out great was toying with engineering wax before the corian but was no where near as good.
Look forward to seeing your wing take shape.