CP, the first third to half of the airfoil means everything. Gauges for the airfoil nose profile really makes a difference too. Also take the wing outside and use a point source to illuminate the wing. (OK, I'm talking about the sun, but where you live that might be a problem. In most places it is a big yellow ball that appears in the sky. Google it, you will be surprised.)

Anyway, with the sun in the late or early sky, hold the wing between you and the sun and slowly rotate it watching the shadow move across the wing chord. It should move smoothly, if not, you have a flat spot.

Sanding blocks are the key to shaping the airfoil. The 3M rubber block works well, and I'd bet you got half a dozen.