Umpire,

shoot at a smaller target. I have a saying I think holds true....it's easier to hit the center of a golf ball than it is the center of a basketball....

Too many people shoot at too large a target....like a pie plate........cut yourself some 1" or 2" squares and place them as your target rather than a dot in a plate....you'll find you aim more carefully and your groups will come together rather than releasing cause your in the plate....don't be satisfied that your in the plate.....rather that your arrows are in a 1" square....it's like picking a hair rather than aiming for the kill zone.....you do this and your groups will shrink.