Brian,

As you know it, Igor's project is a child's boat. He's a helpful person and will send you the plans if you ask him. Yet I would adapt them to adult use. Those thin ply pairs of gunwales better be replaced with double gunwales i-e large ply planks with perforations to alleviate them.
Better use alu tubes or ash stringers.
I'm presently going to assemble alu 21mm diameter broom shafts thru interior tubes.
If I get flex enough I'll build an ultra light with them.
Articulated fir molding stations and polyester sewed skin.
I never build with plans. Such craft are custom-made and build like shuttle-shaped crinolines (not from personal experience).
Measure your hips, pick the main beam stations' length, decide on the stringers' length, join stringers at stems, then "fill" the distance between gunwales at intermediate levels (i-e four other stations).

Eric