A while back I posted a message about methods used to repair soft spots on the deck of my 78 O-Day 25. Some suggested injecting the void with resin. After some concideration I opted to cut into the overhead above the main cabin setty and lay up some new glass from the underside. Worked great. I cut a panel (using a dremal tool) but left the back side attached. Was able to pull down the glass and get enough room to work in. After the repair was done I just pushed the panel back in and wedged it in place with a wisker pole and a mop handle. Let dry a couple hours and filled the gap with fiber glass filler. You can hardly tell.