The Yost design SOF has 3/4 x 1 1/2 gunwales, 3/4 square stringers, and 1/2" plywood frames.
I tried 1/4" ply and it buckled when the skin was installed, so I had to go back and double up the frames around the cockpit.

If I was going to decrease the weight and increase the strength on fuselage style, I would laminate a ring frame instead of the plywood frames. Probably 1/2 x 1/2.

SOF is really tough, unless you hit a broken bottle with a sharp edge or a piece of metal again with a sharp edge.

I gave a young man a long screwdriver and told him to try and puncture the skin. He couldn't do it. I had to take it away and take a full swing with the blade end to get the skin to tear about 1/8" long. However, I handed him a knife (sharp) and it cut thru it like butter.

Personally I wouldn't want an aircraft skin (3.2OZ max) due to handling when getting in and out. The paint or other coatings is not thick enough to give very much abrasion resistance.

Even the fuselage style flexes in waves, that is one of the unique differences compared to a strip planked kayak.

Everything I've read about traditional (non-fuselage) says it doesn't take long to build, but you probably need someone who's done it before.
I've never been in a traditional biadarka or similar style kayak, so I've got no comparison.