This is one of the most common "challenges", or, better, requests my fans come up with. The idea is to cascade two or more slingshots so that the speed is accumulated. While I am waiting for the parts of the "barreled" slingshots to come in (the huge PVC tube already showed up), I am also thinking about tackling this challenge. My current idea is to set up a rail system based in two round rods, 2 meters long, that guide a 1 meter long lightweight slingshot crossbow. The crossbow is shot and glides along the rails, then, with an automatic trigger (adjustable timing), the crossbow is fired while in full motion. The trigger position has to be tuned just right, so the ball would leave the pouch just at the end of the "ride". The crossbow would be stopped by strong rubber, spear gun stuff. Ideally the speed of the crossbow (30 m/s?) and ball (50 m/s?) will add up to a final speed of 80 m/s. This could be a small science lesson more than anything else, plus of course one more "first timer". What do you think?