I always seem to end up doing hammerheads by accident in stall fights in the B-pony. It's usually because I've chopped my throttle and am ruddering to keep from winging over and stalling and it tends to just fall sideways beautifully. One time, however, I had it where the plane did half of the hammerhead, and then just fell to the earth sideways. Have never been able to replicate it, was a very strange spectacle from the cockpit view. Must've started doing the "hammerhead" after I was a bit too slow.