Bill,
I was looking at the pictures on your blog; the ones of the blisters in your hull. I have had blisters on the port side of wildcat for several years. I drilled out the blisteres to drain them. And then, using a dremmel with a bone drill, drilled thru the fiber glass into the core. There was no water in the core. My point is that before you start cutting into the core from inside, you may want to see if there is water in the core at few of the blisters.