When I moved into a new house a couple of years ago I had an empty lot across the street, sheer heaven! Houses are there now, RATS! Anyway I experimented with a series of small designs like this one.

With Depron a curved undercambered shape with the upper surface like the Clark Y works fine. It is not that critical.

I have modified the surface to two flat plates joined at roughly the 30 percent chord point, rounded the wing over the edge of my workbench, etc. and they all work OK, maybe not the best efficiency but they do work.

I also went from a rectangular planform to an eyeball ellipse. The ellipse looks great in the air but is not as good a lifter as the high aspect ratio of the airplane in the photos.

I find a eyeball guess of 3 degrees of wing incidence works and balance it roughly at 30 percent mac and it will fly fine.

They are a lot of fun to work with. I had one that flew fine with four motors but when I went to six the battery drain was so high that I could only fly a couple of minutes. It sounded great though.