I would suspect that the way you offset or helical (left or right) might make a difference in the spin. If it is designed to spin clockwise with a straight fletch and your offset gives a counter clockwise spin....they would counteract themselves. Or (just thinking) if they are offset too much....the air flow might be interupted too much for the vane to work as its intended. If that is the case, your paying for something you're not using. Anyone else. Still, I think it might have possabilities.