This is sort of important at this point in the build. I needed to finish the wing's leading edge by sanding. You can do TLAR or the wing airfoil program (Compufoil) will print out some leading edge guide templates to help you know when you have sanded enough, and not gone too far.
I have seen posts that you can't get a true Clark "Y" airfoil building airplanes from foam sheet. Wish those guys could see me now! LOL.