Yep,, the laws of physics can't be argued, it's just the way things are on this earth. I think Dr. Ashby was more concerned with broadhead design in some of his remarks about penetration in flesh. Your bow will only do so much, pick an arrow that will give you what you're looking for. A light arrow will give you the flat shooting advantage and it will cost you some energy and make your bow noisier. A heavy arrow will give you the most energy to expend into your target and make your bow quiet but you'll have to worry a bit more about trajectory. Somewhere in between the extremes there's an arrow for you