I lengthened a cat by 9 feet by adding to both ends with foam and very thin plywood. Carbon was used in key areas for strength and stiffeners. The result is that the main platform is strong; the ends are fragile; the length is 26 feet; it has 350 sq. of sailarea; and weighs 375lbs. I feel that it is safe in that the ends could get destroyed and I'd still get home OK. It sails great. So I've concluded that focusing on making a strong platform to stay and then making ultra-light ends delivers a good boat that is pretty light.