One of my subscribers suggested I build a weapon like the "Stake Shooter" from the PC game "Painkiller". http://images1.wikia.nocookie.net/__cb20110623175549/painkiller/images/2/2e/Weapon_stakegun.jpg Interesting - seems like the weapon does use rubber, and even has wheels to reduce the band slack/achieve pretension. [ame]http://www.youtube.com/watch?v=PQc7x8eY5Aw[/ame] I am thinking about giving it a try. Of course my version would have to be cocked with muscle energy (in video games crossbows seems to have a miracle energy source coming from out of nowhere). And I would NOT use a sled. Other than that, I think it could work.