I to am using the Miller killers and mine have a 19.6% if I remember right. On my Horton arrows I used to put three thin washers and that would get me around 18 and they always flew better, but I disliked the washers on it. The Italian site that Don showed us and is in the sticky top post talks about this. They recommend 20% for CB's and they report this is the best with the great groups they are getting at 100 yards. My Danny miller arrows fly the best out of anything ever and some is due to the CB, but they also have went into the target consistently straighter then any arrow I have ever used.