Any broadhead, be it mechanical or Fixed blade should fly the same as a field point out of a properly tuned bow. When someone has trouble with a fixed blade broadhead planning and eliminate that problem by switching to a mechanical, the problem was the bow not the fixed blade head. Essentially what they did was remove the blades and tuck them inside the ferrel. This essentially acts like removing the wings off an airplane and storing them inside.
The best way to correct this issue is to first walk back tune the bow. This should be done regardless of the btoadhead. Dial in your 20 pin. Draw a line top to bottom on a target and shoot two arrows at 20, 30, and 40 all using your 20 pin.
If you notice that the arrows do not fall in a straight line down the target say the 30 group is a little left, and the 40 group a little more left, then you need to move the rest to the right as it is obviously throwing arrows left. Don't worry about resetting your 20 pin again, just shoot the same three groups from those same three yardages again. Do this until all the arrows fall in a straight line down the target.
Next is broadhead tuning. At 30 yards fire a broadhead, then a field point. If the broadhead impacts left of the field tip move the rest right. Basically, move the rest in the direction you want the broadhead to go to meet the field tip. The rest movements should be very slight. 1/16 or so.
In the end however, there will always be a slightly different POI of a fixed blade and a field tip. This is because there are blades on the front that the wind can push from the side. Since this happens on the front of the arrow it changes the poi. It should, however, be no more than an inch or two at 40 yards. If you get good enough to stack 2 inch groups at 40 and it bugs you, then just move the sight a tiny bit to correct the POI.
