I used to do the 2" high thing, but changed to 3" high for just about everything except for slow moving lever action rounds. The reason I did this is because I found I was actually shooting over with the 2" high sight in. This was pre-rangefinder and I wasn't able to judge exactly 200 or 300 yards and where I hunt it is very open. I had a terrible time with antelope. I started reading Bob Milek and liked the idea of being able to hold on the animal out to 300 or more yards. I started hitting more often than not and I don't bother holding low if the animal is 100 yards or closer. Their lungs are pretty big. (I usually hold for center of lung.) This year my antelope was a lasered 360 yards and I was shooting my 270 with 130 SGK. Held a little high on the shoulder and took off the top of the heart.
I've been doing it like this for so many years I'd be a nervous wreck if handed a rifle that was zeroed much differently.I use the same rifles back here in the east,with the same sight settings,as I do in the west,have shot a lot of deer under 100 yards,and have had no problem holding on the chest and just killing them.
With hyper-velocity rounds and some of todays really slippery bullets(light weight X at very high vel,like 120-7mm at 3500,and 130 at 3600;and some Swift S'co's come to mind)3" high at 100 yards can give mid range that is a bit too high IME;so I hedge things a bit and 2"-2.5" up at 100 generally gives a 300 yard zero with lower mid range.This works ,too.
