The downturn is actually the only downside , the upside is you don't have to carefully fit the base into the cockpit opening - everything else can be as done as usual.

But your idea is kind of neat, it sure would make a striking and integrated coaming. I guess some router skills would be req'd as you would be swinging an 1 1/2" bit around a soft cedar kayak! (2 x 3/4" inset). If one could bend the 1/4" oak laminations this could be very quick indeed.

-mike