The cross sections looks pretty close to optimum hull with little wave resistance. Thats just by the looks, might be different in reality. Design displacement on 250 lbs sounds quite much - if you are looking for speed you might want to keep the weight down and design it without much load/gear onboard. If you really are looking for speed you could just make the kayak longer. However narrowing the waterline would have good effect on speed.

For stability side the hull might be really tippy with very little righting force at all. Also I don't like the swede-form at waterline - racing kayaks that have swede form in deck have quite symmetrical underwater body. The sides are just raked more at the widest part.

Btw. De Rijp -kayak has wetted surface area of 13.6 ft^2 with 90kg displacement. Just wanted to check that. It's much narrower but chined makes it also a somewhat stable.