another few quick questions about the pendulum sights...why after you sight them in cant you shoot them at ground level..i don' t understand that....also if i' m in a treestand at 25 feet one day and at 15 feet the next day will my acurracy be the same...and finally i' ve heard some people say that the pendulum doesn' t work in hilly country(i' m not talking cliffs but maybe something like a average oak ridge or a vally)....thanks