You need a good helical fletch or at least some offset. The bow needs to be tuned for proper arrow flight and each arrow spin tested to ensure there is no wobble in the broadhead. Mechanicals tend to be much more forgiving and you can get away with not following these steps and still get good flight. Not so with longer larger traditionaly styled fixed blades. You can also check out my link for some more tuning tips. http://www.broadheadtests.com/TUNING.html