I did something similar to this in Salamanca, Spain when I was a foreign student there in 1998. However, our rope was attached to a crane (about 50 metres up) and when you reached the peak of the ascent, you came back down head first and suspended by your ankles. The whole thing was sponsored by Red Bull and basically I got to go for free as the bar I worked in was part of the promotion. I've never seen that kind of setup since, and I'm wondering if it got banned for being too dangerous. I certainly had a sore neck for a few days afterwards, although it was a buzz I'll never forget (not just the catapult bit, but the 30 minutes of hyperactivity after and then a really nice warm feeling!)