: I have heard that two layers of 4oz glass, on the hull would be stronger and
: add less weight to the boat than one layer of 6oz glass.
: Is this due to the 6oz glass wicking more epoxy?

I don't think it'll be lighter but you'll require fewer fill coats since the cloth is thinner. Bigger holes require more epoxy before the layers build up for sanding. My short experience is that if you want light you use less and live with less durability.