Again Aero design events are not held every week in multiple places around the country. As such the risk is lower because it happens fewer times per year with a lot less people involved. Your club events add into all of the other clubs events happening at the same time around the country increasing the risk of a problem if a model is tested during an event. As for testing before or after an event even by one minute the number of people in the potential flight area are a lot fewer than during the event. They don't all suddenly appear and dissapear by the clock. They do however get quite involved in the middle hours of the event increasing the chance of a problem should something happen.

Also I do not recall the Aero events running 3 to 5 flightlines. Correct me if I am wrong.