I have shot milk jugs in the air before, but always with someone else throwing them. It had never occurred to me to throw things myself until I happened to stumble across your youtube video about a week ago.
I was amazed at how quickly it came together after trying it. Of course, I was using laundry detergent bottles, which are considerably larger than your whiffle balls. I'm anxious to buy some of those and give it a try - especially since I broke two flu-flus out of seven hits the other night!