In reality you might not gain anything or very little in the way of speed. Depending on the spine of your arrows you might have to bump up to a stiffer shaft which would mean a proprtionally heavier arrow. The thing you would gain would be kinetic energy and penetration, but just how much is necessary? A 70# bow will blow thru anything and put 10" of arrow in the ground. The arrow from an 80# bow will pass thru and put 14" in the ground. So what's the point unless you're planning a trip to Africa?