Well, it seems that I was not re-inventing the wheel with my broadhead test. Watch the attached video. Dale from 3Rivers does it with a soft (and thinner) tanned elk hide. My hide was full grain so it took more force for my test. He also did his test with what looks like a Magnus head. I think the bones and heavy carpet over the shoulder of a bison warrants going overboard in terms of penetration.
http://www.youtube.com/watch?v=tpHpVR5SUX8
