NigelM i totally agree. My concern with an inch high at 100m, which is what we used to do, so when something pops its head up 50-100 meters from you, you have to guesstimate what an inch or 2 inches low looks like, or whatever your rifle does at that range. Even with loads of practice, though it is easy to measure exactly an inch high on a target of known size, you have to guess the size of the target at range and then guess what an inch looks like on that unknown target. So an inch on an old stag and an inch on a young roe could look totally different in the scope, as you will never have been up to the target and know what size of the target you are dealing with. If a range finder is not used, only the "calibrated" eye, then even more variables are introduced, and without a RF everyone, no matter how experienced cannot guess right every time in varying topography and light. Ok, in most cases it will work fine, and with body shots it will often make no difference, head and neck shots, well i am just not comfortable with that degree of guess works. I expect many here are quite used to this, and find it works perfectly, however perhaps we dont hear all the stories of when it goes wrong. It wont be an issue for SD members i am sure, only for others, who dont use this resource to discuss and learn!
I expect my discomfort with this is because some years ago on a paid for hind stalk we were greeted by a shot over the skyline, across the march, over our heads and coming in our direction, and a herd of reds storming towards us, one with its jaw hanging off, i wrote about it here years ago. We spent the rest of my days stalking chasing the hinds, to finish off the injured one. Eventually we caught up with them, and it was shot at 360 meters. Never a range i would choose, and there is loads more to the story - look it up. However i later heard the shot was taken by very experienced stalker - and it just went wrong. Now, with what is available, i want to minimise all possibility of this, and so my zero is a true zero, as above they all are, and i have no real vertical guess works, and can concentrate on wind effect only. I am not opposed to H&N shots, though it is more a shot taken when no other is available, and there is a reason why i need to take that shot. Of course, enjoy what you do, if it works for you, great. It used to work for me, i was happy with it. Now that i have tried a different zero system i am way happier with that.