My Team has a couple programs that allow for trajectory mapping of the ball including air resistance. It's able to be utilized to calculate the range of scoring starting distances. PM me some info on your shooter prototype and I can give you some numbers, and also the code if you want it.
I'll need the starting height of the ball, the initial velocity, and the launch angle. The program itself compares the Starting distance "x" and shows which range of those values will result in a trajectory that intercepts the goal range, a range of "y" values.
If you give us the information necessary for determining those values for your current prototype, we can help you determine what modifications to either your initial velocity or your launch angle in order to optimize or improve performance.
Many of the necessary equations can be found on this page, btw.
http://en.wikipedia.org/wiki/Trajectory_of_a_projectile
Just an example or two:
at a starting height of about two feet, the optimal angle at 10m/s launch velocity is 40* for the largest scoring range.
At 13m/s it's closer to 35* for largest range of scoring goals at the same starting height.
PM if you need help determining initial velocity or launch angle or any of that jazz.