Tide Craft deck question

[lakehousesanders]

am a new member ,Howdy...just aquired a '96 TideCraft Spitfire..boat runs and handles fine, however under the carpet on the lower deck of the boat the gelcoat seems to have been cut out leaving a sheet of unfinished fiberglass, which is soft. The cut was made about 4 inches or so from the edge and it appears that the section cut out covers the total of the lower deck. I was under the impression these boats where foam filled, if so I'm wondering why the fiberglass would be soft? Here is my main question tho. The edges left in place have been screwdown to the underlaying fiberglass (along the cut tho it seems there maybe old carpet??) leaving about an 1/8 to 1/4 inch height difference. I have to assume there was an issue with the underlying deck , it was cut out and then recarpeted. I've also read there is no wood in these boats...so is the decking under the carpet, in fact gelcoating from the factory? if not what then? if I add 1/4inch plywood , replacing the cutout section, it would be on top of the "soft" fiberglass. my thinking is to fill the cut area with a 2part resin ,and then cover the entire lower deck with a 1/4 marine plywood, carpet and be done with it. any info/suggestions/input you folk have would be gladly recieved and appreciated.....regard to all sanders