I am an engineer and in some of the weather and wave conditions I've sailed in, I've been amazed that our 400lb boats hold together. No doubt that the boats can be made lighter, but I really think that there is a point, right at about 400lbs, where a boat can be made with common inexpensive materials, and survive user abuse and pretty severe conditions. As time, technology, and processes evolve, this weight comes down - we can probably build a 320lb boat to the same durability as 400lb boats were built 15-20 years ago. However, I take comfort in the fact that I can take my overweight F18 or N20 out in steep 3 to 4 footers with 20 knots and not worry that the boat will hold together.