I don't know if there is an upper limit. I was privleged to watch an event put on by the falconers on the west side of MI a few years ago that was a mini-meet and local educational event. One of our clubs young falconers, Angela, took out her RT and about 50 people following. The bird performed perfectly and we had a nice view of an obliging rabbit that flushed then ran down the path that most of the viewers were on with the RT in hot pursuit. The bunny got away, but what a view for the hoard of people following.
Sue