Ballooning off the shoulder's of giants

I would start by looking into Project Horus, reported on back in 2010. They were able to take the balloon to 35,000 meter (21.78 miles on their best attempt) on numerous test flights. Build upon their project and make it better.

Building upon the shoulders of giants is a common way to breakthroughs and pushing a device forward. Their site is packed with everything you need to know.

Cabe

http://twitter.com/Cabe_e14