[merlinron]

bows shoot flat enough these days that sight manufacturers have reduced the range of vertical pin travel, making it necessary to set your sight a bit closer to a height that allows you to use all of the pin's range of travel for the distances you shoot and the height of your peep. you can't always arbitrarily use the upper one or lower one,...you have to use the one that works with your peep height and anchor position. everyone is slightly different, that's why there are two or three sets of mounting hole heights. the flatter the bow shoots, the more critical sight height becomes in order to keep the pin roughly in the middle of it's range of travel . consider that most pins now-a-days are surrounded by a "scope appearing" guard,....you want the pin to be somewhat centered in the "scope" for average distance shots.