in short, you can shoot 6" groups at 20 yards with horrible form, butthe more consistant you become, the better you will become. I stronly believe that "textbook" form is MUCH easier to execute during the moment of truth (on stand, or on the line), than leaning back too far, anchoring way too far back, or just being uncomfortable and stretched out.

Also, poor form can cause stress on joints, shoulder pain, back pain, and who knows what other kind of pain.