I made few interpretations of your original plan v1.3:
– 4mm plywood for the hull, 2mm plywood for the deck (no 3mm available here)
– fiberglass all along the hull inside and outside, 300g/m 45° biaxial cloth. Not so nice to see but very heavy and strong.
– fiberglass on the outside of the deck
– gunwales from one single piece of Douglass fir, without knots and with straight grain all along
– 23kg total weight, for me it’s fine
– one major modification: the keyhole cockpit. Your version for me has the front part too flat, my spray skirt was impossible to release quickly. I use a neoprene skirt that fit my whitewater Piranha Shiva. I tested the kayak with a nylon skirt that had adjustable elastic string but yet I found it difficult to remove the skirt for a wet exit. I added a piece of wood to make it egg-shaped and now it works fine with the neoprene skirt.

Overall it’s a wonderful kayak, I love it! Stable, easy to turn, easy to roll.. you have all my greetings and gratefulness.
I will use the Shrike when I will attend the BCU sea kayak leader course 🙂