I was always under the impression that you zero a gun in the same manner in which you will be using it. I've never seen a lead sled at a match, nor in the woods while hunting. Basically, if you sight in your gun while standing on your head then you need to take that shot at the deer ( or match target) while standing on your head! otherwise your hit will be off. Just my "old school" way of looking at it. But, whatever works for you, go for it. that's why we call it a free country. Well,,,,,sort of,,,,,kinda,,,,,,maybe,,for a while anyway.