The potter decks were 1/2 balsa with an asymmetric layup. More material topside for penetration resistance. Not a lot below. I have a pic and notes on this. Let me see if I can find it. Probably my "Bass relief" thread.
Here it is: post #63 in the Cape Cod Crusader thread:
http://www.classicseacraft.com/commu...ad.php?t=25061
You can guess how many layers that is. I haven't dissected it. But you have thicknesses, so that can get you there.