Taylor, All is not lost. I have a 1978 T30. We redid the decks some 5 years ago. There were some smaller areas of wet core (stuff is like oatmeal) where we opened the deck like yours. After cleaning up everything wet and letting it dry we replaced it with more balsa core soaked in epoxy, fiber glassed over to replace the skin, faired it and them pained everything with new non-skid (Kiwi Grip). Came out well and is strong as a rock.