Thanks Alex. I've always found this one awkward, so inspired by your tutorial, I gave it a blast this afternoon. Unfortunately, I found my usual problem, in that I had trouble getting a clean release/exit from under the arm. After a bit of experimenting, I wondered if it might be the orientation of the ken at release that was foxing me. Indeed, it turned out that if I released the ken with the string hole facing the back of my arm, it would exit with a twist or a wobble. But if I released with the string hole facing away from my arm, I managed to get a cleaner release, and a smoother flight on the aeroplane to finish. (String hole sideways seemed to be tolerable too.)
I hope that helps someone else to nail it.
