Well I' m no expert but will say that I currently shoot an foc of 8 out of my 4runner extreme and have yet to have anything but a pass thru out to 35 yds. I shoot GT 5575' s and their web site recommends min. of 8. The way I understand it is that at longer ranges (45+) this helps the arrow maintain altitude and speed?! The shaft ends up being pulled rather than pushed.I would say that it would be more important hunting big game at longer distance. Then too there is the old addage " IF IT AIN" T BROKE DON" T FIX IT" !! This being the case with my set up I' ll shoot it. But would like to know if the info I have is correct???