Give it a try....
Hi,Several of the boats in our fleet have had the decks repaired. You could try filling effected area with epoxy and then redrilling the holes through the deck. The old open areas that delaminated will fill at least partially with the epoxy. To start, just remove the hardware, drill out the old holes a little oversized, put some very sticky, duct tape over the hole inside and start injecting some epoxy into the hole from the topside. The epoxy will seep into the surrounding core area. Once filled and hard, redrill your holes. I would then buy some aluminum angle stock at Home Depot and make over sized backing plates to cover as much surface area as possible below. This may give you enough support. If you do need to repair core, cut out the headliner inside, not the deck out side. This si a rather messy job. Not overly difficult, just takes time and patience. From what sounds like a very low purchase price, you probably don't want to pay the costs of a survey. You know what you have.... A lot of boats are out there sailing with soft cores. You just need to be sure the deck hardware is secure and won't pull thru.Good luck,Paul