Tom, it sounds like you need to trim them some, to me. To get a better handle on it, you should try more than one shaft, and shoot them enough that you are confident that they shoot nock right when your form and release are good. 15 m is far enough, IMO. Getting consistent results from your bare shafts is more important than the distance. When you're satisfied that the shafts shoot consistently nock right, start trimming!
I use very soft furniture foam for bare-shaft tuning, to prevent breakage of the shafts when the spine is off.