Physics Lab - Sling Shot Precision Targeting?

[celestial ninja]

My physics class is getting groups to launch a baseball from a slingshot (which he provides) a horizontal distance of 40m to hit a circular target 1m in diameter lying flat on the ground. The ball has to travel this distance in the air. We're not allowed to practise, and he says that AIR RESISTANCE CANNOT BE IGNORED. We can make measurements, like the spring constants, etc, but that's it.

What calculations should we do to get the baseball on target? How can we ensure accurateness? ie launch valocity, spring efficieny, does the energy input equal the energy output, stuff like that...

I'd really appreciate any and all help - if you could even direct me to some good helpful websites, it would be much appreciated! Thanks!