Well gentlemen, I couldn't take the suspense anymore. I pulled back the carpet and chipped away some wood and although the wood cam out rather easily, the wood is dry underneath, except for a small patch just above the fuel tank. I took a hollow pole and drove it through the foam all the way down to the hull, and the foam is clean and dry. The hull in the section underneath the rot seems dry. The wet spot I spoke of earlier was part of the stow located under the walkway to the bow.
I forgot to bring home my dial guage, but realized that I could just close the middle window and watch the clearance between the window and the frame. The hull seems to flex about 1/8" with the bow moving up and down about 3-4 feet. I was in some mid size swells at about 20km/hr. Once I got it on plane, flex was not so observable, until you hit a random wave, then once again about 1/8" max. There is about 1/4" clearance between the window frames whether the boat is in the trailer or on the water.
I am starting to question my assessment of the stringer, as I was in a hurry and drilled the hole out at dusk. I didn't feel any wetness to the wood, because not a lot of it came out. I said it was wet because it looked wet. The color was a little darker than I expected, but I think that I was expecting it to be rotten so I didn't spend enough time there.
I have to wonder if a fuel leak caused the wood in the floor to get soft? Would fuel vapour cause the plywood adhesive to disbond?
I am going to drill another hole in the stringer during daylight and get a better look at the wood.
It looks like I may be moving backwards in my 12 step process. Heading back towards denial........