To determine weather or not your canoe is too light depends on what you intend to use it for. As is, it obviously works well enough to at least float you, and it will likely hold up fine unless you intend to abuse it. I would either add more ribs/cross sections to support the relatively light chines, or beef them up (to 3/4" x 3/4" perhaps) if you want to stick with three cross sections. I used 1/2" x 3/4" WRC chines on my SOF canoe, but I have steam bent ribs on 6" centers and think they could still be better supported... Your gunwales are probably ok, as is the keelson.

I'm interested to see how you turn it into a folder.