Good point(s) MD. While I don't try to take out both shoulders on a broadside shot, if I can hit one of them on an animal that's facing me or angling away, I've found that helps too.
I've seen deer class stuff go down pretty reliably with a lung shot that hits the rear lobes, but the bigger, tougher stuff does seem to have an amazing ability to go long distances in really mean country with such a hit. Even watched a Pronghorn hit through the rear lobes of the lungs try to get up a minute or two after going right down. It really pays to both shoot carefully and to make sure he's down for keeps. E