Stop aiming. The Shield is a close range point shooting gun. And if you hit the assailant five inches low and right, you take out a kidney instead of a heart. Perfectly fine shot.
As far as I know, the only way to adjust windage is to tap the rear sight a tad to the left/"driver's side" in the dovetail. Elevation is tougher in that it will require a shorter front sight or taller rear sight.
