I've done a few of those Hobart things (OK, 10 of them) and only once did an aircraft cause us issues and that was when a AS350 gave a spinnaker a shake when hovering very low and to windward of us. The wash from the spectator boats was far far worse chopping up the seaway.
I like all was always pleased to see the aircraft when miles out to see. It meant that A. Somebody was near (in spirit anyway) and B. You were going to be on telly! My favorite of course was Gary T in the ABC AS355. He often appeared in the early light or late in the afternoon.