I'm hearing what you are saying steve. My first seat I made was carved out of a boogie board front end. It was nicely curved upwards (bow of the boogie board) which I thought was a good thing. In practice, the upwards curve was unsupported and actually sloped downwards.

Result. When I first started paddling in my new homemade kayak after a break of a few years and a tweaky back problem, my feet went numb. I just figured I was an old and damaged 44 year old and that was what would happened after 20 minutes paddling. So I used to stop often and stretch alot. One day after a particularly exciting 40 minutes session I jumped out of my kayak stood up and fell down straight away into the water. Odd I thought, so I stood straight back up and fell down. Oh, uh,things are looking pretty bad here.

However, I picked up a thread on the bulletin board about numb legs and the solution for me in the end was to prop up the front end of the boogie board seat with some foam glued on underneath. Result: I can sit and happily paddle for hours without my legs going numb.

Your seat looks pretty good. Just keep in mind the front edge needs to be a bit higher than the butt, bit like a car seat (note, they are all tilted up at the front).

Good luck and happy paddling. With enough tweaking, you should be comfortable and be able to concentrate on the scenary and not your legs numbing up.

Cheers Pete