All the documentation I have read stresses the following...

Never change the pitch, length, or chord of the propellor. If you have to sand to remove weight, sand the curved side of the prop to be flatter.

The static balance of the prop is one thing, but when spinning, the prop generates thrust. The thrust is a function of the airfoil shape, pitch, chord, and length. Having one side of the propellor (or one part of the propellor blade) generating more thrust than the other side can have a more damaging effect, and cause more vibration than having a statically unbalanced prop. An Ideal prop is both statically and dynamically balanced, but modellers do not have the resources to spend the $$$ required to get dynamic balancing eqpt.

Back to the prop.... The thrust of the prop is a function of length, chord, pitch, and airfoil. Changing the length, chord, and pitch of the prop all change the dynamic nature of the prop way more than the airfoil shape. So, to change the static balance of the prop and have the least impact on the dynamic balance, change the airfoil shape ... sand the curved side flatter.

gus

P.S. See http://www.bollyprops.com/propbal.html