....Despite the massive gravedigging (lol), I'd be happy to answer that.
Slingshots are generally a bad idea due to the lack of control of the poundage per square inch, or draw weight poundage. Although...
http://www.basspro.com/Hyper-Pet-K-9-Ka ... reen/BlackOur park has actually classified something similar (above) as a crossbow, so I don't think we would allow it for spellballs. Fuzzy is currently making one to look like a blunderbuss. The launcher is perfectly safe, and I personally have been shot with it point blank at it's version of full draw. I'll post an image of the final product when it's done.