In looking at a picture of an airplane whether it be model or full size it would be difficult to see the difference in airfoils between root and tip. Some of the old pattern airplanes used the same airfoil for root and tip, but when people start looking for more performance out of an airplane the wing is one place to look. Using a variable airfoil is one way of fine tuning the airplane. I designed a sport Cap 10B once, and it had a very different airfoil at the tip as compared to the root to get the elliptical shape. The higher percentage of thickness of the tip will help with the slow high alpha type flying. Tom