Depends on the deers state. If he's extremely edgy and nervous I have aimed at the hair line of the belly and struck them dead center. If they're relaxed I always aim for a hair probably 1/3 of the way up the body. Longer shots(30 and beyond)at relaxed deer I aim center of mass. Gives me a little more hedge for distance misjudgement. I've found deer beyond 30 seldom drop. If they hear something they don't realize it as danger and more often than not just look when the bow goes off. Below 30 I really try to feel the deers nervousness state. Slam dunks, I aim for what I want to hit but it's usually below center line. A lot depends on the angle.