And my explanation there would have been page 1 of the 5 page technical discussion.
So here are the pics I have saved of me, what do you think of the chest angle? Some but not enough?
Pretty good, though there's some issues with your CoG not moving forward early enough. Your hip rotation comes late in the windup, and so the hips are not into the court as much as they can be. The trunk twist also comes in a little late, which manifests in a slightly higher knee bend.
Pretty easy to remedy. As soon as you initiate your toss, start aiming with your chest, even before you release the ball. This may seem counterintuitive, and you may be afraid of screwing up your toss. But, in actuality, this will give you an even more quiet toss. And this will also accentuate your hip and trunk rotation. You may even see something approaching a back arch, though it's really not that at all.
There's also variations to the visualization:
1) When serving from ad-court, you can aim with the left chest. When serving from deuce-court, you can aim with the right chest.
2) If you aim with your collarbone (again, observe left and right for respective court), you can also get a boost in pronation.
3) This is kinda unrelated. But if you want to try out a "Djokovic arch", then try initiating the toss holding the ball somewhat pointed to the ground. In other words, before you release the ball, you have to rotate your tossing forearm so that it's properly pointed to the sky. When you do this, this also causes your service arm's forearm to rotate, and that in turn causes your upper trunk to "arc" a little. This also gives you a much lower racquet drop, though it doesn't really improve power.