This is the short version. If your arrows are properly spined and your muzzy's are flying like field tips, you need to tune your rest. Out of a tuned rest with properly spined arrows nearly every fixed blade head will fly like your field points.
Moving to a mechincal head because they hit with your field points isn't the best route. Using mechanical heads to cover up a tuning issue compounds the problem and hurts penetration and broadhead performance all the way around.
go to
www.bowjackson.com and check the easton archery tuning guide for broadhead tuning...
This should get you fixed up.
Good luck.