Great looking sling. I'll have to make a new one soon. I tried staff slinging, it is a blast, and it too amazed me how deep the stones would bury themselves in the ground.
The sling is one of the great forgotten weapons of ancient times. I think I read that they have the muzzle velocity of a .357, and they literally smashed armor and helmets, and were preferred over bows. You also cant see a sling bullet coming at you, unlike arrows.