So, again, to close out my side of things, let me explain once more in excruciating detail why *focusing* on the first bounce on your side is misplaced in the terms of giving special advice about *serving short*.
A *Short serve* is not determined by where the first bounce on your side lands.
If you practice serving a lot, you will look at a lot of things about to serve to understand what spin is on it and how it is traveling. One of those things will be where the serve bounces on your side because it is part of the complete serve trajectory.
But when learning to serve short, there is all kinds of advice out there. There are some people who say that the first bounce must be close to the net. There are some coaches who will tell you that the plastic ball has changed this and the first bounce must be closer to your endline because of the plastic ball. But a high level player told me that a coach told him when he was younger (which will be 20 years ago or more) to serve close to his endline for *all* serves, including short ones, because it made them faster.
Brett, who is an incredible server, told me that if you want to practice short serving, use your visualization to imagine the serve bouncing just behind the net on the opponent's side. Then with your skills, practice repeatedly. Of course, Brett also believes that most players can't serve tight (low, spinny and short) unless they are 2500 and that even world class players have trouble doing this upon demand under pressure. Brett taught me that the most important return to learn is the forehand loop of long and half long serves.
Part of the reason why many players can't serve short is that too many coaches keep giving bad instruction about what makes a serve short. The focus is always on the first bounce on your side when that has nothing to do with whether the serve is short or not. The key is that however you practice your feeling, and no matter your touch, the first bounce has to be close to the net on the opponent's side. OF course, with heavy backspin and some sidespin serves, you have room for more error because sidespin gives longer trajectory and backspin tends to want to slow down. Topspin wants to roll forward but the touch is harder. But if you can find a way to serve short topspin with the first bounce on your side close to the net, then do it. I don't think it is easy or possible, but you may find a trick that can make it happen.
When you use the firsts bounce on your side as information, but not as the determinant of serve length, good things happen. When you use the first bounce on the opponent's side as very important, fantastic things happen. Because you are focusing on what really makes the serve short.
If you want to raise your deception, you may do some interesting things like try to serve your backspin so that it bounces a little higher like topspin so you can serve high topspin and remain deceptive. Both can be short and deceptive if you focus on the first bounce on the opponents' side. You can also push down when serving topspin so that it travels low like backspin and then try to serve your backspin serves with more speed but with the first bounce close to your endline but fast enough to look like it is fast topspin serve. These are all possible when you know that you can play with your serve trajectory given your target of serving the ball at a specific point on the opponent's side. And while you need to practice a lot to get this control, it is easy to start doing it when you understand what really keeps a serve short.
So I implore you, please stop repeating and focusing on outdated advice about the first bounce on your side - the first bounce on your side is more related to SPEED, not DEPTH. Note it, but always stress to the serving student that what keeps the serve short is usually the first bounce on the opponent's side. The faster the serve you serve into the short zone, the better, because it usually means the serve is lower and gives the opponent less time to decide.