Thanks for that ShyTorque (fantastic handle by the way!).
I am inclined to agree with you in regard to the ceiling for r/c a/c, but think it is a stretch to account for the delicate control which would be required from the ground. To be able to match the helicopter height would in itself be difficult.
I appreciate what you say about the 'wake pattern' (for want of a better expression) caused by the turning rotors. The way that I picture it is like a hollow doughnut or toroid which itself rotates in the same direction of the blades. This may be completely wrong, but it does make sense to me.
Incidentally, there was a report in June from South Wales of a police helicopter encountering a UFO, and it later turned out that there was a wedding in the general area at which Chinese lanterns were released. This was not reported as an Airprox for some reason but it did reach the media (with the same hype from the same person cited in the article which started this thread). If anyone wants more information about that incident, details are at:
South Wales Police helicopter UFO incident 8th June 2008: Invasion of the bobby snatchers
cheers,
Joe