Next time you have him on his back, pick him up by the feet and carry him around in front of the girls upside down. Reportedly, this helps tremendously... (I've never had to do this myself so far, but I will if and/or when opportunity knocks). Another thing is if he mounts one of your girls in front of you, chase him off her. (I have done this!!) Letting him know you won't tolerate that kind of behavior leads him to believe you're in charge - it's no less than THE top rooster would do if you had more than one in the flock.
YOU are the top "bird" and need to show him that. Right now, he's not convinced. All else fails? Freezer camp.
YOU are the top "bird" and need to show him that. Right now, he's not convinced. All else fails? Freezer camp.