While there are many ways of doing things all the top competition shooters will normally set there sights so they can see what they are shooting at, once you cover up what you are aiming at you may drift off target.
Personally I use a florsent red dot that is 3 inches in diameter hold the top of the front sight at the bottom edge and "0" that way at 100yds. This gives just a bit of leeway if you misjudge the yardage a bit. Lee