I'm slowly changing over to 2.4, but today I wanted to fly the Avistar and it's on a 14 y/o FM Hitec Flash 5. My Hitec Flash 5 works just fine. At my field, almost all fliers are on 2.4 ghz so I find my old radio in some respect to have an advantage. My flights were without incidents. Old FM radios are fine as long as batteries and servos are up to date. In my opinion.