My son recently purchased and 1979 Catalina 22, in the recent past it was severely damaged on the starter side in just ahead of the cabin - adjacent to the forward hatch. On the topside of the deck all appears okay, while the underside of the deck has been stripped to the core. This makes back portion of the deck pretty flexible. Our plan is to tried to replace the expose core, refibergalss the underside using West system epoxy and cloth. Then glass in a gunnel to gunnel stringer on the underside adjacent to and immediately fore and aft of the hatch. The core appears to be plywood, we are assuming this is a marine grade plywood. If we need to replace core material should reduce plywood or is there a new core material that would be better? A second the problem we have noticed is that in a couple of locations there appears to be a bubble separating the inner scan of the hull from the core. These bubbles appear to be about the size of dinner plates. Any suggestions on how to repair these bubbles? Thanks, Skip