You're right that there are a lot of variables. One that you didn't really mention is the use of glass. On my S&G Mill Creek I only glassed the outside of the hull and put tape on the seams on the inside of the hull. There is no glass on the deck at all. All per instructions. So it has about one third the total glass that a stripper would have. That's a significant potential for weight savings over a stripper. I've heard of some S&G's being built with no glass other than tape at the seams. There's enough strength in the plywood that you can get away with that. (Of course, with no glass on the bottom of a hull, even a few sandy beach landing will wear a hole in the epoxy pretty fast.)