One of the questions I see pop up from time to time is how much lycra do I need to make a swing. It all depends on what your set up is where you will be using this and the person using it as well as the quality of lycra you get. In our case probably 5 ft is more than enough but you must take into consideration tying the knots to hold the clips and so forth. Usually you get a couple knots in there. We have a typical 8' ceiling and the hooks are placed anywhere from 1ft to 4 ft away at the max. My kids weigh about 35lbs and 50lbs.
The nice thing about having too much lycra is the other possiblities you can do with it. You can put it up in different ways so you could take it and hang it up like a hammock. You could also hang it up more like a cocoon. You could have a child lay across it so they're folded in the middle if you sew up areas on each side for a STRONG bar to go through and be hung. (I'll have to post a picture of this because I'm not explaining it well at all.)
If you take the time to get the knots out the lycra could be used to wrap and tie around your child so they can push against it while sitting down kind of like putting your knees in your shirt.