I think that the red mark on the Mathews grips are just a referance point and that each archer's hand position and form will determine the correct center shot. My personal best center shot position on my Mathews bows are 7/8" from inside riser the the center of the shaft. Also think paper tunning is actually over rated; but a good starting point. Shooting from 30 to 50 yds and tweeking the center shot has gotten my bows to group their best with both field points and broadheads.