I've hit them in varying degrees. Everything from dead center to just catching the thinner cartledge. I've had varying degrees of success... from great to just plain crappy. I've shot them with everything from recurves to 80 pound compounds. From point blank to further out. The total summary of my experiences would lead me to say, don't do it if you can help it. I've had more real successes but it only takes one bad one to leave a bad taste in your mouth. If you stick the rib cage you got your deer. It's really that simple. Center the ribs and go start dragging within minutes. I won't even go into the destruction and the failures I've seen with shoulder hits because I don't want to give anyone a false sense of invincibility. Stick to the rib cage.

Last year
Shot my 6 point quatering away and blew through the opposite shoulder at 42 yards. Arrow didnt not initially pass through. It stopped at the fletchings, but was pulled out about 5 yards after the hit.

80 lb bowtech liberty.
Generating around 77 - 78 ft lbs of KE.

My son this year shot his buck in the shoulder. It was quartering TO him. I told him to not take this shot in the future. Problem is he is shooting and xTec at 70 pounds. Not sure on the arrow weight but it is the CX 300 Camo with Grim Reaper 125 grain heads. It went right thru the shoulder and thru a rib on the exit side. Very hard to convince him that it was a poor shot to take with that kind of penetration. The buck went about 60 yards and dropped. I am not a user of mechanical heads but they did work great.