My wife shoots 37 and 38 pound bows. Every deer she has taken the arrow either passed through or was sticking out the other side, except for one two years ago. It was shot with a Darton that is 42 at 28, she draws a little over 26". The deer jumped at the 14 yard shot and caught the deer in the ham. The Grizzly stopped at the far left scapula, about half of the broadhead went into the scapula. I make sure that her arrows fly perfect, 420 grain cedars, and the broadheads are as sharp as I can get them. Her new bow has better cast, but she past on a buck this year that was too alert, so she let it pass by. All of her deer have been taken from the ground, scared of heights, I think the ideal range and the angle has a lot to do with her penetration and recovery success.
Something to be said that if one has a 45 to 50 pound longbow at 26" everyone will think it is enough, but a 38 pound NAT that puts out the same arrow faster is questionable. The number on the bow is only a starting point, The arrow is more important in the lighter ranges. It has to do its job perfectly. An arrow shot under drawn will fly loggy, if the person gets a predictable clean flight from a lighter bow, it will have more killing power than the bad flying short drawn arrow from the heavier setup every time. I think that if we were honest with ourselves we can all agree that things like short draws happen when shooting at game when shooting more weight when that first cold shot is taken. Byron Ferguson said that he likes to hunt with bows that are a little shorter to cover himself for that accidental short draw.