I like the idea of using hatches, such as this Mako Boat Hatch Door, I found on ebay for $129.

Thats a cardboard template I cutout so I could easily mark the cut line.

It was the largest I could find. It measures 35 1/4 long x 20 1/2 wide. Sure it may be a little expensive, but you get what you pay for. For installation all you have to do is cut the hole and screw it down. The aluminum frame provides all the strength needed to reinforce the cutout. Though I did add some aluminum angle under the piano hinge.

The hatch door is made of starboard. When I sit on top of the vee berth now it feels much stronger than before, I can site right on the hatch, no problem and I weigh 200+, very sturdy!

Heres a pic of the aluminum piece and how its installed from underneath. The aluminum piece will provide a good attachment point for the forward bulkhead of the internal compartment, that I will build.

I plan to use hatches like this in other areas of the boat as well, such as the settees, for additional dry storage. I like the Tempress hatches because you can buy drop-in inserts similar to a rubbermaid container, and when the hatch is closed it provides a watertight seal due to the rubber gasket. Which would provide more floatation in addition to the styrofoam pieces in the boat.