I used 2" thick blue foam insulation for floation below the decks. I used most of a 4x8 sheet, providing about 325 pounds of positive bouyancy. In a capsize, this gives a nice safety factor on top of the already slightly-positive bouyancy of the hull itself. I think the foam floatation sits too high to allow it to be pumped out unless the water it is flat-calm, so I have sealed the bulkhead lockers in the hopes of floating it a little higher in case of a capsize on a choppy day.