: If I use 1/2 Baltic birch ply for the frames, what is the minimum thickness
: (outside edge of frame to inside edge)?

Btw, from painful experience if you choose to use Baltic birch plywood for the frames make sure it really is Baltic Birch ply, there are lots of cheaper both in price and quality substitutes around right now. I've got a really nicely cut out set of frames for a Sea Ranger that started delaminating in the shop from one of the substitutes, junk.

Bill H.