How do you arrange that?
easy, get a gas can, fill with gasoline. Grab one tennis ball, soak in gasoline. Get 1 piece of pvc pipe with the same ID as the tennis ball. Stuff gasoline soaked tennis ball inside PVC, tape one end shut as a bias ply with 9 rolls of duct tape. Pour a little more gasoline into tube, aim at head, set on fire......you should this point hear a big "Whoosh!" and the tennis ball will come flying out......this is where it gets tricky. As with most unrifled barrels the PVC is not going to be an accurate barrel. You'll have to work at aiming it directly at your head. If all steps are followed correctly you'll have a nice divit in the side of your skull, and quite possibly have set your yard on fire, unless you're working in your garage, which I sometimes do, in which case you'll burn the house down. Beware, you may want to leave the cap off the can of gasoline and hold it just under your chin for full effect. I make no warranties expressed or implied with this mod, you do so at your own risk! Good luck and happy tennis balling!
Oh, and if you can swing it, get someone you don't like to stand right next to you, then the mod will work twice as well.
Dan