I noticed that one of mine has a split in the bottom (cheap plastic!). I used to make combing boxes for my sailboats out of plywood--not that hard to do--I made the flange out of teak. Glassed the inside and that way you can have what ever size you want. Also a plywood box would give some stiffness to the side of the cocpit. I don't know at what point there may be some structureal component of the cockpit walls. But most of us note that the boats seem to flex, and develope stress cracks just aft of the cabin. I suspect that some of the "box section" of the cockpit gives some increased stiffness. I certainly would not cut out all of the fiberglass in the sides--on the other hand, I doubt that any "engineering" went into the amount of cutout which is currently present.