CORD,
I think you are really into this slingshot thing <img src=icon_smile_big.gif border=0 align=middle>
The main advice I can give you is to use the muzzleloader balls as ammo. Marbles lack the weight needed for most game and most shots. Weight= more kenetic energy= more knockdown power. 50 or 54 caliber balls are best. Remington ammo is the stuff to use becuase it is not the dusty lead that can make you sick, it is brass colored. As far as aiming, shoot it like a recurve. Pull it to the corner of your mouth and shoot instinctive. A constant anchor point is needed to be accurate. Trust your instincts. Good luck and keep your shots close. Aim for the head on larger game, the neck for squirrels and rabbits. If you go too far back you got shoulder or forward and you got head. Hope this helps.
"Hey ya'll, watch this"