I think optimal bullet performance is one that landed on the off side stuck in the skin. That's the most energy you'll ever get out of a bullet. Because no matter what bullet you used it was all spent inside the animal in the most optimal preformance. I tend to like pass throughs also for tracking but not much tracking needed if it was hit in the vitals.

I too make some bullets Head but there's no question why nothing moves after hitting it with a 400 gr bullet. Hehe.