Cameroo, What a great looking baidarka (or ikyax)! That's fantastic! It will be interesting to see it all skinned up. I'd like to build one of those too, for longer touring and camping.
Adirondackman, Alot of people (myself included) follow the building instructions in, "Building the Greenland Kayak: A Manual for It's Construction and Use". The book doesn't offer a fixed set of plans, per se, but describes the process and construction methods, and gives a range of dimensions relative to your body measurements. The construction is very fluid and there are forks in the road all along the way. Once the gunwales are laid out with markings for the deck beam and rib locations, there is very little measuring involved, with most of the pieces being custom fit to the kayak. There are several simple little wooden measuring guages the book describes to mark the pieces.
A couple of words of advise if you follow this book. The range of height/depth measurements that the book describes will give you a kayak that is fairly high volume for a Greenland kayak. On my first build, I stuck with the mid-range to smaller size dimensions and wound up with a very stable touring kayak that had room for minimalist camping gear, but it was too big to roll all that well, since I flopped around too much inside the cockpit. That seems to be the general consensus among builders. If you prefer a more snug fit or want to advance your roll, you'll need a more snug fit. So, you could shim such a kayak out with foam or build one to much smaller dimensions than those described in the book. For example, the suggested kayak width is "the width of your hips + 1 or 2 fists", depending on how roomy you want it. I built successively smaller kayaks and am happier with my current kayak width of "wdith of hips + 1/2 fist" (or an 18.75" beam for my 17" hips). I went with similar downsizing for the kayak depth and masik height. But then again, I like a snug fit and like to roll, and don't mind a twitchy kayak too much.
Also, I would recommend "not" using the aft cockpit beam as a back rest, as it will dig into your back. Either keep it back slightly and pad it with foam, or better yet, keep it way back and install a commercial backback or do without. (I prefer to do without.) Similar to the footrest deck beam, be sure it is far enough forward so you only hit it with an extended foot or it will cause cramping. Again, there are commercial footrest options, or you can err on the side of caution and dowel in a piece to extend it after the frame is together, if needed. In my current kayak, I set the footbeam far enough forward that it's just barely out of reach unless I sink my lower body forward, so I have no foot or back bracing; which works fine since I'm otherwise locked in the kayak tightly between the gunwales and the low masik on my thighs. Save your finished cockpit/foot/back beam locations, so you have a base to hold or modifiy for your next kayak!