The Morris boats are indeed traditional so they tend to follow traditional ways of sizing the construction methods and the weight ends up where it does.

Platt was an interesting guy but he was a bit of a belt and suspenders engineer, the frames are light but with lots of extra reinforcement which adds weight. Still his little canoe like boat is very light.

You can build SOF's light, my modified Yost Sea Ranger at a bit under 19' long and with 3/4" ply instead of 1/2" for the frames (I misread the plans, oops) and with my first try at my Dacron/glass cover still only weighs 34 lbs. It could easily be build well under 30 lbs. and that's for a 19' long kayak with the Dacron/glass cover. Want to get silly and not worry about the cost can be fairly easily built under 20 lbs.

Bill H.