I am now to the floor stage of my project. There are cracks (2 hair line 2 foot long) in the floor where it seems a little soft between the stringers. It is only the floor which seem a bit thin. There is not any wood below in my boat (69 15' MFG) only in the transom which has been replaced and behind the dash. What would be the best way to repair? Plywood, mat and glass? The floor is so thin you can feel every stringer and they are solid. Any suggestions? 