I looked at the video of Sampras serve motion over and over again in slow motion from different angles. What strikes me about his arm motion was that after hitting the ball at the highest point, his arm breaks down with his elbow, not his shoulder. I can't help notice it looks like a "windshield wiper" motion, where his elbow is the center of the windshield wiper. It looks like a windshield wiper moving from back to front, with his elbow as the center. The windshield wiper ends on the right side of his body. Start on the right, ends on the right side. Now, my question is, can we hold the right arm up, and practice doing this windshield wiper motion with elbow as the center, windshield wiping back and forth, back and forth, until it is engrained in muscle memory. What do you think about this as a serving arm exercise?