This from Nick's description of the GA:
"The cockpit is large and roomy making getting in and out easy without having to be overly limber. The coaming narrows at the front so the paddlers can get their knees solidly under the deck if they feel the need to brace themselves solidly into the boat."

If you can get your knees "solidly under the deck", you might not need to add any knee brace constructs other than a couple of pads of minicell foam glued strategically under the deck, sort of like wedges with the thickness oriented towards the cockpit opening, and cupped for your knees/thighs. See the link below for some ideas and variations.

You sound like a tall, thin guy. You might need more in the way of hip braces like what you see in Kurt's Cormorant picture to keep you centered in the seat for stuff like rolling. If your knees/thighs can get a grip under the deck, any padding there is more for comfort as it probably won't need to be too thick. Just so you get a solid purchase.

Forward sweep roll seems an easy one to learn, but in this boat I suspect you might have good results learning a C to C roll, especially if you are using a Euro style paddle. Kurt is right, when you learn to roll, all your paddling and bracing will improve since you'll have confidence to lean and push the envelope. It's just plain fun.

Good luck!

: I'm putting in my recess cockpit now an like the look of building knee braces
: right into the recess. The thing is I really don't know exactly where to
: put them and if I really do need them afterall. I understand their use in
: giving you extra purchase in the boat to aid in stability, rolling etc.

: I know it's a matter of personal preference, however I'm a newbie to this
: sport and have little experience to fall on. I doubt if I'll be rolling
: this boat anytime soon, if ever. My boat is the Great Auk and I have cut
: out the Guillemot cockit modified to 31" long by 16.5" wide. To
: get some sort of simulation of what the braces will be like, I've sat on
: my cockpit template and also measured the height from the cockpit floor to
: the recess height at about 8". In the sitting position with my knees
: fully extended, I've determined that my knee caps would be 3" or less
: from the bottom of the knee braces. At my knees, the cockpit total width
: is about 10 to 11 inches. Is this about normal? I guess a tight fit is
: what you want for the best control?

: My height is 72" and 155lb, from what looks most comfortable to me, the
: knee braces need to be mounted as far forward as possible. I do realize
: they will make getting in and out slightly more difficult. If I decide in
: the end to not add the braces, it seems a piece of foam just under the
: coaming would be just as effective. Thanks for any ideas.