neureotex;

You are right. With the straight wings, undercambered, Clark Y(flat bottom) , 1/3 from the leading edge would get you in the air.
But when it comes to canards, deltas and swepts.......out the window that goes!
There are massive calculations you can do for area, density of material....blah blah............modeling clay is easier!
If it'll glide, it'll fly.........
I did the 1/3 rule on my first delta, 10" SkyRay.....added clay, no gear, to the 1/3 rule. Gave it a chuck and it backed into the ground after the stall...........
From there on its just a history lesson.

Tony
ARS Software & Innovative Solutions
http://www.falcon1.net/~ars/rcmodels.html