A slightly imballanced prop puts an added vibration load on the aircraft if nothing else.
I agree with Mike and aim on this one. What I will say, though I've never done it, is the best way to resolve an imbalanced prop would be to put the heavy blade opposite the piston when it's top dead center, that way the imbalanced prop offsets some of the piston weight. That will give you less vibration than a balanced prop.
Dennis-