I sealed off the lazarettes on Tattoo from the space under the footwell. I enclosed the space under the foot well to be water tight after installing the floatation. At the lowpoint of each lazerette I installed a plug (like the one for the forepeak) that can be removed from the cockpit (as opposed to the cabin side). Water can be drained to the bilges by removing the plug and then pumped overboard with an electric bilge pump, or pumped overboard (by hand) from the cockpit. Although the Bomar hatch covers are supposed to be water proof, mine leak even though they were well sealed at installation. The water comes from the rain. After an all-day heavy rain there is an inch or so of water in each lazerette.
So, to keep stuff out of the water, I made a floor for each lazerette. You can see how simple they are. Just a piece of 1/4" plywood with just one "leg." Works just fine. The volume under the floor is almost trivial.
I'm trying to understand why my hatches leak. I think it may be that the gaskets were not made to ward off "standing water" that accummulates at the aft end of the cockpit before it bleeds outboard through the weep holes in the combing. My plan is to raise the hatchs by installing a "bezzel" of about 3/8" thickness between the hatch and the cockpit deck. If standing water doesn't exceed 3/8" it will be ok.
Suggested solutions would be appreciated.