Have you considered scaling down and using a golf ball, smaller target and work on the design in
minature for now? I still think repeatability will be an issue without careful attention to the things I've
mentioned.
IMO in basketball throws the hands don't do much, the ball is too large/heavy for fine wrist- and
finger-control, you tend to lock your hands into a fixed cup and work from the elbow and shoulder
for distance throws.