Here's more-or-less where I'll be putting foam and sealed lockers in order to make this boat float in case the sea gets in. Blue lines represent 1" thick foam panels with luan plywood skins, skinned and tabbed in with glass to seal it all completely. Solid blue areas will be solid foam, glassed in. Anchor locker is getting split in two horizontally, the area where the rode will lie will be sealed off from the boats interior, and will drain directly overboard a la Geoff's "Uhuru" and Frank/Adam/Howards #50.
I'll be reducing the area where water can lie within the boat, nearly filling all bilge areas and sump with foam - my thinking is that if there is seawater aboard, I wanna know about it, and get it overboard. Also, less space for seawater means more space for floaty foam.
Same for under-bunk/locker areas; basically, wherever there is a V formed against the hull, I'll put a foam floor in to make the bottom level at least partly.
Also, I have been playing with 3" thick piece of test foam directly against the hull, seeing how much *usable* area I lose with that thickness. It ain't much. If I can go with 3" thick from the stringer down, all the way through the boat, that will give me 48cu/ft of the the estimated 55-60cu/ft needed to float the boat if she gets holed.