The main problem is when an entry point is observed water repeatedly entering that hole throughout the season can delaminate the foam from the hull and the gap created can hold water. The closed cell nature holds it there, so if you have multiple entry points, you have multiple pockets of water, plus the foam will absorb it a little (in a severe case).
I redid a boat bottom a while ago, tried to let it drain propped up for a YEAR, and it never got dry. Eventually just cut the bottom off, and found pockets of water at all water entry points. That situation is a bit more exaggerated in severity however, but wherever a little water got in, the cyclic action of pounding waves (flatbottom boat) made the water 'cut' through and delaminate the foam creating air pockets that filled with air across the hull at any leaky point (the hull had three metal strips that were riveted on for protection against hitting debris in the water... big PITA)
It is what it is, but at this point, I'm done talking about it. The way I see it, I'll use 2 lb foam and gain 5 lbs, or gain 1 lb in reinforcements and not use foam at all, and put on drain plugs with a well sealed tray area (like FL-crackers).
At reference to a previous comment about ping pong balls weight causing a difference in buoyancy needed, 10 lbs difference out of 280 lbs isnt going to cause much buoyancy difference, and the 51% packing efficiency meaning HALF the guarenteed buoyancy isnt enough for that offset 10 lbs. Pingpong/foam? It would work, whats it worth to you?
