Thanks Chris,

It's exactly as you said except there is just core under the winches, etc. I'll use Corecell foam and have most of the cabin top rotten balsa removed and am starting to install the foam with proper bevels on the edges structural epoxy in bolt/screw holes. Predictably some areas were better than expected and others worse. The deck is next, followed by the cockpit. It should make the boat stiffer and lighter.