we did this on private property in a very controlled environemnt...fire dept. was on hand.... I used electric matches and a custom electronic sequencer a friend made that I triggered from my transmitter. The shells were just attached to the heli, no tubes..I didn't want them to go away from the heli....
I don't think this was anymore dangerous than fireworks in general!!! One scene, which is not on the trailer was when we set the 22 shells off on a helicopter, I did not intend for the heli to survive...but it did!
I just think this would make a great addition to traditional firework shows... NOBODY has fireworks that are this directional

Even just straight night flying without fireworks ont he helis would be entertaining, particularly while everyone is sitting there waiting for the show to start! I hate the down time associated with watching a big show...
I am the only person doing this in the US, doubt it is being done at this level anywhere else in the world. The r/c helicopter community is quite tight, and I would know about it.
Mike
www.mikescolesheli.com