I wanted to respond to your question first. Now I want to respond to something that CBM SC said regarding arrow spine. CBM did not say he agreed with the statement, he only stated what others have said.

There is no such thing!

An arrow is either perfectly matched in spine to bow setup, or it is not. You can sometimes get an over-spined or under-spined arrow to fly good and to hit the mark by number of feather/vane, size, and type used; and by tweaking other gear, but such a setup will always be at the edge of the envelope, inconsistent in performance, and extremely vulnerable to the slightest mistake in form, release, and certain environmental forces.

If some Bowtech shooters are getting consistently good flight and good accuracy out of arrows that are over/under spined, those shooters are doing something that is compensating for bad arrow performance, and they may not realize they are. Or, the shaft selection chart vs. the setup they are using is incorrect.

Remember, a shaft that is under/over spined, and is having its flight being corrected by other means, may be trying to swap ends and is loosing speed down range. Also, contact angle on quarry may be off from center and cause decrease in penetration.