My instrument instructor pointed out that I’ve been saying “Four Seven Fox” instead of “Four Seven Foxtrot”. I realize I’ve been doing this for years now, but this is the first I’ve ever been called out on it. I don’t usually fly a plane with an “F” in the tail number but now my regular club plane does end in Foxtrot so I want to fix the habit. For how common it is though, I found surprisingly little commentary in the (FAA) FAR/AIM or on here. I hear it all the time on radio, but that doesn’t tell me if ATC finds it bothersome or how bad it is that I've said this however many times.
Is abbreviating “Foxtrot” to “Fox” acceptable for ATC comms?