:: These boats, because they lack bulkheads, do not lend themselves to
: re-entering the boat if you capsize and can't roll. Even with
: float bags mine submerges completely if I try to use a paddle
: float to get back in. Solo paddling + No roll = no SOF boat, in my opinion.

True indeed about the surprising amount of water that can be taken aboard, even with float bags. However a sea sock completely eliminates that particular risk, allowing no more water in - or usually much less - than a conventional kayak with cockpit bulkheads. Definitely a great investment (or you can sew your own) with most any SOF kayak.

For lumber, consider MDO (medium density overlay) plywood (NOT OSB!!). It's not quite up there with BS1088, but of much higher quality than most any other product. Plus, it is readily available - even if your lumber yard doesn't stock it, they can order it quickly and relatively cheaply.

For lumber, again, check out local lumberyards, rather than big box stores. There's usually a few in even a medium sized city, and they don't necessarily cater only to contractors. They often have, in my experience, a better selection of dimensional lumber - and plan to spend some time sorting through the stacks!

For lumber, again: www.Woodfinder.com and http://www.glen-l.com/resources/lumber-suppliers.html

Good luck!