See Agassi http://www.youtube.com/watch?v=lXWks8yvRJQ&feature=relmfu look at 1-2 seconds in, 22-23 seconds in, 41-42 seconds in. First thing leading arm back is his elbow. Hands and racket head still between shoulders. See Fed http://www.youtube.com/watch?v=vCm6OIjbPr4&feature=relmfu at 4-5 seconds, 17-18 seconds, 26-27 seconds elbow is leading back. All I am saying is if you lead back with the elbow it keep hands and racket head to your side and prevents laying the hand, arm and racket head back early. If you keep the pointy elbow until you start forward, it will also keep your swing shorter. Both Fed and Agassi keep pointy elbow position until they start forward. Elbow is pointing first at back fence then at players back and stays further back than hand and racket head until they start forward.