What Ed said, in a close paraphrase, as I recall, is that mixing feather and broadhead torque "could lead to decreased penetration." I suspect Grizzlies work even with "wrong" twist feathers because they have high ME (long narrow profile, smooth ferrule, etc.), are real hard steel and the El Grandes were until recently among the heaviest glue-on heads you could buy. The goal is to have the head twist as much as possible as it passes through an animal. This splits bone, creates an effectively longer cut channel, does a lot more damage in soft tissues than a straight punch-through, and "twists and slashes" hide on the way out for a larger exit wound. A good single bevel will overcome the opposite twist of fletchings, which is much slower. But why make it stop and reverse direction when you can give it a headstart with matching feathers? Soon enough many broadhead makers including Grizzly will be offering both L and R single bevels, so unless you need broadheads immediately, now is a good time to wait for the new offerings. That's what I'm doing. Dave