Since no one else has replied up to this point I will offer a couple of points that I have witnessed as deal breakers when it comes to fun flys. And that is simply too many events. The set up times between events and events that are excessively complicated, this often requires to many helpers.
The number of helpers if excessive can be problematical also. This especially so if they want to participate .
I believe the biggest event breaker is just too many events. I have done wingless trainer races in the past and they were the most successful type of event but it was only the races and nothing else. They were relatively simple to run and only required two cones about 100 feet apart out in the center of the runway.
John