I am not sure about the weight of the cloth, epoxy and hatches. I will try Bill Hamm's method of skinning. 2.5 oz Dacron (Diatek) from Aircraft Spruce will be applied, heat shrunk and sealed with epoxy as a tight firm base for a layer of 4 oz twill weave fiberglass, epoxied on to the Dacron, as if it were a plywood hull. I will try to make lightweight hatches. We can compare notes on weights when our boats are done,
Peter