I would discourage a head/neck shot. Too small a target area and too much to go wrong. An elk shot in the jaw or thru the wind pipe will put miles of rugged terrain between you and it far faster than you can imagine. If you don't find it the animal will die a long, miserable death and go to waste feeding coyotes and ravens. The heart/lung region is a large, lethal target area. From backbone to brisket a mature bull averages 30" in height and from back of the front leg to the diaphragm runs around 18" with a mature cow being 1/4 to 1/3 smaller. Go with the high percentage kill shot, not a high risk shot. Yes, yes multiple respondents will reply claiming to have killed rail cars full of elk with head shots. That's not my experience in actual field situations. Live with your decisions. I hope you make the right decision the first time. Enjoy the hunt.