CaptDavid,
I assume you are planning on transverse bulkheads; where are you planning on putting them, and how high will they be? My 20 is not as stripped down as yours, but I've got the tank out and I was thinking of doing something with the exposed foam (it's damp on the bottom) and installing bulkheads to make the tank "coffin" area tight and sealed off. See my earlier thread here
http://forum.classicseacraft.com/sho...b=5&o=&fpart=1