I can't imagine the penetration would be worth a flip on a target. Too much cutting surface. The larger the cutting diameter of a broadhead, the poorer the penetration. We've used 2" mechanical broadheads in the past with good luck. Video's kindapoor(first attempt at filming), but we put the edited down version on our website.
http://www.backwoodscalls.com/pics2.html,and click on thelink for "Opening Morning 2005". Just limit your shots to 20 yards, and anything will work fine. Just hit 'em where the wing joins the body, dead-center the spine, or Texas heart shot. The trick is to get to the baseball-sized vital area in the chest. It's alot harder to hit the head than the body, but I guess if you miss him you miss him.