Arthur - while I agree with you that a deer twisting its body is probably due to hearing shot noise, an arrow hitting and cutting flesh will cause an autonomic response of muscle contraction. Think of how fast you jump back when you get a shock of static electricity. You have no control of it and it happens VERY fast. It' s supposed to be even faster in animals. I' ve read many articles by archers who hunt African (large and dangerous) game and many of them use skinny carbons (heavily weighted, of course) because of their better penetration. I' ve even read one article by Chuck Adams where he stated that he felt that a skinny carbon has a penetration advantage. (I should have saved that article, he doesn' t say it too often.)