LAST EDITED ON Sep-08-13 AT 01:01PM (MST)[p]Back yard field point flight is not an indicator of an arrow leaving the bow square as it relates to your form. This is why a low profile mechanical will mimic (to a degree) your field point impacts.
When you screw on a high quality fixed head like a Shuttle T, Slick trick, etc AND it flies like crap, then that is an indicator that your heads are 'catching wind' as it comes off the string. At this point your fletching is trying to stabilize the erratic flight (which it cannot) and your broadheads impact different from your field points.
So, 1)you either have a form issue (grip/release), 2)your arrows are assembled poorly or otherwise mismatched for your setup, 3)fletching contact, 4)or mechanical tuning issues to sort out (assuming you want to). Its as simple as that.
Why does it matter? Because even with your field points and mechanicals, your arrow flight is still porpoising or fishtailing. To a degree this is true even if you're not observing it. Broadheads don't create the above flight characteristics, they simply magnify it. If either (or both) are happening, then your arrow is just as likely to impact tail-right/left or tail-high/low, as it is 'on center'. This is akin to striking a nail with a hammer that is at an angle, which reduces force directly behind the head (penetration), and increases lateral forces (bad).
Listen, most guys don't even care enough to start to understand the above and most get by just fine. So do whatever floats your boat, just trying to assist.
Bill