I have had one set of arrows out of a Super Kodiak, tapered cedars with 160 grain Magnus two blades, do a side step when shot in a tailing cross wind, with a vertically mounted head. The next arrow was horizontal and it was dead on. After the shot, while I gave the deer sometime before tracking, I retrieved the wayward arrow and shot it again and it did it again, found my other horizontal and it flew straight, tried a different vertical and it side stepped as well with the trailing cross wind. This was my only time that I noticed any difference in flight, but I prefer vertical for aiming purposes, I find the horizontal at times distracting.