I must confess I just guessed the contour for my wooden seat for the canoe called Dora - see http://theancientkayaker.weebly.com/ - but it is fairly comfortable. I based the contour on a garden lounger I made years ago, but forgot to allow for the additional hip support needed for a kayak/canoe. The back hinges down for car-topping, although it can be removed easily. The odd top was intended to be used for comfortable exiting; the seat slides forward so I can recline the back until the top shelf is horizontal, and I planned to slide my butt up the back and onto the shelf. Being a canoe, it turned out to be easier to just step over the side in shallow water. Kayaks present more of a challenge to the geriatric paddler! I made it from left-over bits of red cedar and a few bits of pine for contrast, even the hinge is wood.