I've heard that if one is going to sand one of the blades, that it is better to sand the front of the blades because the back of the blades is what does the work. I think the idea is that from a purist standpoint, any sanding changes the shape of the airfoil, however slightly, and it would be better to change the shape of the front of the blade because it is less critical than the back of the blades. I have only heard this by word-of-mouth and don't have any documentation or articles that have studied it in detail.

-Ed B.