While replacing wet and rotting end grain balsa along the both sides of the cockpit on my 43' DCFB, I found something I did not expect.
Since I was using a moisture meter I found high readings under the stern port cleat and this was not due to an aluminum backing plate. I removed the cleat and the outer fiberglass skin. Underneath was a balsa core and the inner skin which was no more than one layer of woven roving and a couple layers of mat. That was it!! The balsa under the cleat was moist but otherwise intact.
I removed all the balsa which was 5/8" thick and replaced it by laying up multiple layers of 17 ounce biaxial and West epoxy. I then mixed West with 406 Colloidal Silica and layered this on top of the new glass and placed the original fiberglass outer skin on top and put some bricks on top while it set up.
BTW, I used Coosa board to replace the balsa core. I used 1/2" Coosa and made up for the difference in thickness of the 5/8" thick balsa by adding extra layers of Biaxial...it is very strong!
Jon