well the bullhead does have those big old wide blades acting like fins. If your bow is shooting everything else right I imagine it is in tune. As long as the bullheads are grouping nice and tight i would just move the pin to the point of impact and then move it back when its time to shoot regular broadheads. I don't know if that is the most scientific answer but i think it is the easy one. The bullhead is quite a bit different then a regular head and i'd be willing to bet thats the cause for the different point of impact, i doubt all the tinkering in the world will get them to have the same point of impact. Just my opinion though, good luck i hope you get it figured out.