I am wondering if I am shooting to little spine with the arrows I have. I am shooting a 400 spine now. Depending on what chart you look at I can shoot a 400 or a 340. The more I look into this the more I think I should be shooting a 340. I was shooting 65# and again, according to the chart a 400 would work. I have since went to 70# (BH's were hitting low and increasing the poundage brought them in) and it appears that I may need a stiffer spine arrow. I still shoot good groups with what I have but I was thinking that a stiffer spine might stabilize quicker. I am shooting 70# at a 29" DL with 100 grain heads. The arrow I am shooting is and Easton Axis ST. I am not sure of the speed as I have not chrono'd the bow since moving up in poundage.