Bob,

On the boat planking shrinking over time, I saw an interesting study a number of years ago in WodenBoat about that subject. The gist of it was that if wood is allowed to fully expand and contract over time it loses nothing in size or strength. However, in a boat, the planking is constrained from swelling to its full size by the other planks. The net effect is that if not allowed to swell to its full size the wood then shrinks to less than its original size. I don't remember all the technical details but the conclusion stuck in my mind. No solution for it that I remember but an interesting read.