First off, I want to say that I agree with heavy and foc, but I think that most of you guys have too much time on your hands. An accurately placed arrow of most any reasonable weight will do the job every time. Yes i know that you are preparing for the marginal hits... they happen no matter how good you are, but preparing yourself for the complete pass through arrow is an exercise in disappointment.
No matter how much weight you shoot, no matter how heavy your arrows are, you are not going to pass through every time.
I have shot deer, pigs, moose and bear with 55 - 92 lb bows and.. I have a very long draw (32"s) and usually use a 10gpp arrow and I can handle it...it doesn't handle me.
It will always come back to placement. I can't tell you how often I have had critters bleed profusely and die in short order, but carry the arrow to their death and that doesn't include off side shoulder hits. I know guys doing the same with much lighter tackle.
Shoot what you can get to fly well even if you shortdraw, pluck, or do everything right!
BigJim