care to offer some clear cut solutions for that takeback?
So the basic things you want to about the arm movement
1) Primary movement: lateral (across the body)
2) Secondary: elbow starts to hook upwards (or moves away from midline of body)
3) Preserve elbow bend through the takeback portion. Don't straighten arm.
4) NO forearm rotation.
5) If this is working for you, the racquet face should open a little toward net, between ground and net and racquet tip should be pointed toward right side fence.
Best way for now is to just isolate that part of the movement (i.e. just work on swinging forward and coordinating with the hips.) Don't worry about the ball toss, trophy, or upward swing. Just concentrate on getting the shoulder rotation down (and keeping the front shoulder below the back shoulder.) If the rotation is correct, then you should feel as if your pinkie is pronating the racquet arm.
Gotcha. I see you all have been working hard analyzing the takeback and I agree that setting up properly makes finishing (in this case pronation) much easier and more natural.
I confess this is the first time I've really tried to do this through a computer. I admire instructors like you who can make these descriptions so clear without, you know, being "hands on."
Once you feel that this is good, then add back in the 2nd half of the service motion and work on ball toss and upward swing.