It looks to me by your information you have most your information right in front of you. You know your grains per inch, you know your arrow' s length, you know you tip weight. Most 4" vanes average around 7.7gp vane. So you got a real good idea of your weight. You say your hitting low & to the left. What about paper tears now after your adjustments? What about your Forward of Center on your arrows. Cutting your arrows back another inch or so, depending on your rest style can have effects on FOC, and Spine. Both can have effects on paper tears low & to right or left. www.eastonarchery.com go to the Tech Room for eastons tuning guide. This will help answer your questions.