Aim low. Your perspective changes when shooting from above. On the level, if you aim mid body, you pretty much center the lungs. From above, because you can see most, if not all, of the off side of the critter's back, and less of its underside, if you aim middle part of the body that you can see, you'll hit high. I'm convinced that this is the main reason folks hit high when shooting from above, moreso than not bending at the waist. Bending at the waist does keep you from shortening your draw a bit, but at the relatively close shots we take (20 yards and in) a slightly shorter draw really doesn't make a notable difference. Aiming too high is the culprit.