One of my novice technicians was working on a bow tune the other day and told me that he couldn't get a particular spine to work. He told me that it was too weak a spine because of the tear he was getting. I asked him how he knew that and he quoted the Easton Tuning Guide. I proceeded to show him a few tricks and the arrow tuned perfectly. I told him that the ETG was a good reference, but that it was ONLY a reference. I showed him how other considerations have to be addressed to properly tune a bow.