I don' t see why some people think it is so difficult to compensate for drop (or " rise" for that matter) with one pin.
CG, I understand what you are sayng about a 2" drop between 20 and 30 yards with YOUR setup. Heck, the pins would probably be too close together anyway. But not everyone who shoots only has a 2" drop.
Heck, I use three pins and still have to adjust slightly for in between shots.