Thanks John.
Bill, I will try to keep the weight as low as possible. Thinking of glassing over the ply bulkheads with light glass/epoxy, and sealing the edges to the hull skin between the longitudinals with thin strips of foam and PU caulking, after the hull is skinned and do the sealings to the deck after it is glassed, through the hatches, which will be two 8" inspection screw-on hatches, + one larger hatch for tent etc right behind the cockpit, yet to be designed. That is part of the fun, figuring these things out. I will use your method of skinning. May omit the glass layer on the deck if trials show that just the 2.7oz uncertified Dacron (From Aircraft Spruce in England) is strong enough. I don't anticipate the kayak crashing upside down onto rocks.
Peter