I've spoke with Paul, too. He sent me a few to try out, too. I have to get my drop away set up on my bow before I can try them. But anyway....He said to test the penetration was to take a deer hide and stretch it out far enough in front of the target so it will clear the hide before it hits, then shoot a fletched arrow and a FOB'd arrow through the hide and see which one penetrates more. I'm gonna give it a go since I have 10 hides in the freezer anyway.