People are often surprised when they see how thin the wings and fuselage of a light airplane are, too. But they confuse bulk with strength. In reality, the situation is more complex. As with an airplane, each bit of weigh savings reduces loads in other areas leading to further possible weight savings. (And it works the other way, too, of course: Each unnecessary weight gain increases loads in other areas resulting in further weight gain.) For example, when the bow hits a wave the resulting forces are directly proportional to the mass of the boat because they are the result of the wave trying to decelerate the boat, and F=ma. Keeping the hull light allows less sail area, which allows lighter rigging, which together allows less ballast and, in the end, you have a boat that's much lighter and therefore experiences much less force when it hits a wave. Combine that with vacuum bagged, oriented fiber construction (rather than the chop fiber used on a lot of older boats) and you have a hull that seems thin and flimsy to someone accustomed to those older boats, but is plenty strong enough for its intended purpose. Nobody would claim that a Mac 26 is a blue water boat, but they're plenty strong enough for how they're meant to be sailed.