I was at a Roger Waters concert last night and he had the faithful old flying pig of yore that is powered by three gimbal-mount fans and has been for years. New to me since the last tour was a flying sheep that had six simple fixed-mount propellors strategically place that was doing all the work including some pretty impressive aerobatics.
I'm thinking maybe I'll try to mock something up with a smaller balloon and that Sparkfun IMU I have that's gathering dust.
You don't want to be a sheepskate, include enough. You'd better be able to calculate quickly, in case you need to make a ewe-turn and get the flock out of there to avoid calambity.