I've used my slingshot quite a lot in the last day. Range affects accuracy, as does elevation difference. Just outside the current flee range seems to work pretty consistently. Triple that and it gets pretty tough to hit anything. If you watch the trajectory and adjust, however, you can usually nail them with 3 or so tries.
I like the pull from about 1.5 times flee range. Gives me time to line up an uppercut as they charge in.