My experience is very similar to redline' s. I spent all spring and summer shooting 4" offset vanes and was very pleased with my accuracy out to 60 yards or so. When I put broadheads on, I expected them to shoot the same since I knew the bow to be well tuned. Surprise--they were low and to the left and not as tight.

After trying numerous fixes, I fletched some arrows with 5" vanes--some with hard right and some with left helicals. To my relief, that fixed the problem. I' m now shooting 5" hard right helicals with a dropaway rest. They shoot slightly to the left of my field points, but very tightly grouped. I' ve adjusted my sights accordingly and have arrows identical to my hunting arrows for practice.