Upper body tilt - slice serve vs. kick serve

#1
Shoulder-over-shoulder motion (aka cartwheel motion) results in the tilting of the upper body towards your non-hitting arm.

you have to hit the ball towards the 2 o'clock on the ball for slice serve, whereas towards the 12 o'clock or 1 o'clock for kick serve.
How do you achieve this?
You can achieve it by either abducting your shoulder more for kick serve, or, alternatively, tilting your entire upper body more for kick serve.

I'm inclined to think that the proper way is the latter - by keeping your shoulder abduction angle constant regardless of the type of serve and instead adjusting the upper body angle.
The reason is that pronation of your arm becomes harder and even painful when your arm is abducted beyond certain angle.
The "optimal" upper arm abduction angle, I think, is close the one created by pitchers throwing fast ball.
Thus, if you want to change the hitting spot on the ball more towards the 12 o'clock position, you'd have to tilt your entire upper body more towards your non-hitting arm.

Now I can't find any video or analysis on the internet to support or disprove my point.

Can people chime in on my analysis?
 
#2
I don't know the variety being used for the shoulders' orientation for the kick serve, but it is more complicated than just high and low shoulder. Stosur is especially acrobatic and may not be typical. Look especially at her shoulders and how up down they are, the line between the shoulders seems about vertical. However, the camera angles can be deceiving. She also does seem to have her ear toward the ground and other videos show that she and some other servers have this head on side appearance.

I can see the racket going higher after impact so I believe that this is a kick serve. It is always best to also confirm the kick serve with the flight and bounce up and to the right.
 
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