I have a friend who tries to add more power into his serve by jumping. However, he jumps too much into the court as oppose to more straight up and a little forward. This causes him to hit the ball more behind him, since his body is already way into the court while his toss is only about a foot into the court. He would land with his left foot about two feet pass the baseline. I have tried to correct him so that he lands just pass the baseline or at most a foot pass it, but is is not working. Can some experts/instructors who have had experience with this give me some advice, whether visual, technique, drill, etc. that would help him correct his jumping.