So far, every deck penetration that could be done wrong was done wrong. I found that the little snap fittings for the bimini had been pop riveted (and many had failed because of using aluminum with stainless). Those that had been replaced over the years also had leaked. All have now been removed. I only found a couple of bad spots in the balsa core, and those appeared to be discolored rather than rotten. Again, with the balsa core moisture at full saturation, it is difficult to identify exactly what was leaking. I didn't find anything that made me want to tear off the fiberglass laminate (from below) and examine, but then I'm also really reluctant to go there.