Ashby's most recent (2007) studies show that all his "parts," and EFoC in particular, provide a higher percentage of penetration gain with lighter bows than with heavier. Like you, I shoot mid-50s in r/d recurves with arrows 650 - 740 grains and with the right broadhead they shoot plumb through elk, even hitting ribs in and out. I don't know that you need that kind of bone-busting power for deer or hogs, unless you tend to make shoulder shots, but if you can shoot them well at huntable distances, why not? I shot over the back of a a beautiful Coues deer buck last month because I went down in arrow weight thinking that's all I needed and could shoot flatter and faster farther, and I practiced. But in the heat of the hunt, my hand-eye coordination returned to the heavy arrows I was accustomed to and I held too high. It would have been among my proudest "trophies." I will never again switch arrow weights for particular game, but will shoot the same heavyweights for everything, from bunnies to bull elk and moose. Why do you ned 34" shafts? What's your draw length? As others have noted, that helps with FoC, but it totally screws up my instinctive aiming. Wish it didn't. Dave