Glad that you like the airfoil, but don't blame the tip stall on the Eppler... lots of things could cause that (including airfoil, admittedly).

I kitbashed a 4*40 to take the Selig, so that I could see how it performed. My intention was to compare it against a stock 4*0 that I also had.

It might have just been me, but I 'seemed' to notice an increase in speed from the stock airfoil (not sure if that was real or imagined), but it satisfied me enough to want to use it for my scratch-built scale plane.

For the record, I don't think that Dr. Selig gets any royalties for this. I think that he puts his airfoils out in the Public Domain for everyone to use just because he likes to do things that way. From what I can see, he's developed a lot of airfoils, especially for gliders.

Bob