I wouldn't put foam under the floor either. Bouyancy under the floor makes your boat far more likely to roll and float upside down if you swamp it. All that water is sloshing around in the cockpit above an "air tank". If the buoyancy is high under the rear deck and the water can flow quickly into the underfloor compartment it lowers the centre of gravity and the boat is far less likely to roll. That gives you time to pump it out too. I see this with fisherman. They roll their boat at sea and all they have to hang onto in the open ocean is the bow eye. I would rather be sitting inside my swamped boat, floating the right way up, waiting for someone to figure out I am missing. This is far more effective with a high sided boat like yours than a low sided boat with a heavy powerhead jacked up high in the air. And yes..... I have rolled a boat full of water while racing … :rolleyes: