I write this with some reluctance.
After all, why would you need any help giving your short opponents a hard time? Isn't being short tough enough in any sport?
In tennis, being short isn't all bad. Short players can handle low balls and balls hit into the body better than tall players, and their quickness and agility compensates to a large degree for some of their most obvious weaknesses.
One weakness that accompanies short arms and legs is lack of reach at the net. Quickness can compensate substantially, but short players are generally easier to pass or lob. You can pull them up to net by hitting them short balls, but you'll want to make sure that your short ball either stays very low or very short. Any short ball that sits up and gives your opponent time to hit it at a decent height will probably be hit too well to give you a chance to lob or pass, and your short opponents will often have more time because they'll get there quickly.
Once you get the short player up to the net, an ordinary, flat lob might not be enough to win the point. She'll just run it down. Amanda Coetzer will chase down flat lobs all day. Any time you get your opponent running back to retrieve a lob, you should go to the net yourself and challenge her to pass or lob you. You'll have the advantage, but she can turn the tables again with a good lob of her own. If a lobbing and chasing duel proves better for her than for you, you might want to use a topspin lob, which even the quickest player usually can't retrieve.
At the baseline, your short opponent will be vulnerable to balls that land fairly deep and bounce high, especially if you hit these to his one-handed backhand. Use topspin to get the high bounce, and if you get your topspin lob working well, mix it into your baseline rallies once in a while. Your opponent will be forced to back up and hit from a defensive position, unless he has the skill to take your ball on the rise, as Andre Agassi does especially well. Agassi's height is average, but he has the small, quick steps of a short player, and these help him with the precise positioning needed to hit so well on the rise.
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