Incorrectly benchmarked in bowhunting, KE has absolutely no indication of penetration or for measuring the tissue destruction protentional of projectiles traveling less than 2500 fps. In fact, KE was never intented to be used to messure arrow penetration (read more here).
Momentum is king........and is statistically significant in prediciting arrow penetration.
We wanted to post a momentum vs kinetic energy calculator here so you can figure out the truth behind the penetration power your set-up is generating.
Compare numbers and you'll see that fast light arrows don't come close to the momentum of slower heavier arrows.