I mentioned this same thing to my Martin dealer and he told me - No. But like BG stated somewhat: What is your definition of efficiency? Is it accuracy, speed, quietness, etc.? And how can one actually state maximum settings is the most efficient? If a bow is set at its maximum draw weight and draw length you are utilizing 100% of the bows usefullness thereby its most effectivness. But for me, I too shoot my 70# - 30"bow at 64# and 28" draw. I can shoot 4 -5" groups at 70 yds so to me that is the most effective. If I crank up the weight, it is uncomfortable and my accuracy drops off.