Black Frog is right, Rangeball. The wingspan method is a good starting point and will normally get you to within 1/2" or so, but it is not set in stone.
As long as your resulting drawlength feels comfortable and you are set in a complete "T" with no leaning or head-craning one way or the other, (perfect form) then the world is yours, only you can decide what feels best for you, my friend! <img src=icon_smile_wink.gif border=0 align=middle> Good shooting, Pinwheel 12