Er........ surely if your group is 4.5" low, then you've got to RAISE the backsight - if you're using the backsight as the zeroing medium. And on the VERY rough ready reckoner method that 1 click equates to 1" at 100 yards (it doesn't but it's sort of close in a sort of average sort of way.....) then to raise the group you've got to RAISE the backsight by 2 or 3 clicks. No?