The question of building with foam strips has come up before here, but as I recall, no one had any expertise to share. Check the archives on this site just to make sure.

It seem you are set on using foam, but do some looking into stitch-and-glue boats as well. You may be suprised how light-weight a wood boat could be if you used 3mm Okoume and lightweight fiberglass cloth outside and only fiberglass tape inside. Some to look at would be Chesapeake Light Craft's (www.clcboats.com) North Bay and Pautuxent in 19-foot versions and Pygmy Boat's (www.pygmyboats.com) Osprey HP. These designs could probably be built with slabs of foam sheet as well. My Pygmy Arctic Tern, without hatches and bulkheads, weighs 36# and is built with the standard lay-up. Going with thinner wood and cloth I'm sure I could get it down to less than 30#.

fer waddever it's worth Dean