I, personally, am very confident in my shot placement. Therefore, I always ask myself"how deep is deep enough". I have watched annually as my younger sister kills bull elk after bull elk with her 52 pound bow. Her penetration is absolutely nothing in comparision to mine (I pull and shoot 405 grain arrows w/ a velocity of 290 ft/sec from an80 lbs bow). Fact of the matter, each bull she has collected is just as dead as every bull I've ever killled. So the question is: how deep is deep enough? I like shooting light and fast. I want my arrow to hit exactly where I'm aiming- period!Reaction time (jumping string)of the animal is greatly reduced by a fast arrow, Thus my arrows usually hit where I've intended. Sure, I'll take a pass through whenever I can, but honestly, how deep is deep enough? How much more dead do you want them? One thing for sure, they won't die (OR YOU WON'T FIND THEM) if you cannot hit 'em in the right spot.

Find that arrow combination ( mass/ velocity) that works best from your rig. There is no one right answer....TOO MANY VARIBLES!Be proficient with your equipment and enjoy your time afield.