From what I have taken the draw length can determine arrow spine, but I don't know how much it affects it. I try not to over think it. Yes Chuck, I shot with a D loop, release and anchored with a kisser in the corner of my mouth. I just want to make sure that I can get all the variables that i can control in check as I start this tuning process. One thing I have learned, tuning is difficult because unlike the compound, it is very hard for me to repeat the exact same things every shot. But, that's what makes this so interesting and fun. I do not get discouraged, I embrace this.