Shake down cruise. Hold on!

[FishStretcher]

Wet foam can be heavy, but at something like 8 lb per gallon, hiding 60 gallons of water to make 500 lb in the stringers if they already have foam in them might be a bit of a magic trick?

But wet plywood core in a deck might be 150ish lb more than a dry balsa core in a potter hull. That's guessing at 3 cubic feet of core in the deck. One at 64 lb per cubic foot, the other at 10.