note to all 'beam' builders out there....Plywood is VERY strong when on edge (vertically).4 layers of 3/8th ply would give GREAT strength as long as the bottom edge was 'trimmed' out with wood so as to keep it from deflecting for/aft under load. I know little about boatbuilding,but in home building we often use plywood as an additional laminate when building a beam to increase the compression strength. WAY stronger than conventional wood.