I've read the Phys Tehc of Tennis, and done so, rather thoroughly. Maybe not some of the later sections of the book, but there are some interesting things to consider when we talk about high racquet head speed and weight addition.
To say that adding weight to the racquet on faster strokes has diminishing returns is, well honestly not totally wrong, but not entirely true.
In fact, I've begun research (thanks to
@saleem) to investigate a bit more indepth about the vibration node location. And as many who have played with adjusting recoil weight (or just simply adding weight to both tips of the racquet) can attest, where you add weight changes the nodes of the racquet.
As we know, the most elite players in the world tend to have weight added under their bumper. It's one of the best locations for weight addition (imo for many reasons). Now as most people should recognize (most MRT's will immediately know this), this raises the node locations. By decreasing the distance from the node to the impact location, you always increase power. The other thing that happens as you hit closer to the tip, is you increase the actual impact speed of the racquet compared to lower on the frame. Although in most factory racquets, the energy return at the ~25" location is low, it goes up when you start getting into the higher swing weights, and goes up very noticeably (you don't need any special tools to notice the power bump). This means (and you can check this with the TWU shot creator) the location which gives you THE MOST SPIN, becomes more powerful.
So increasing swing weight goes beyond just increasing the angular inertia the racquet can transfer, it has a multi stage effect. Which is why fed etc can go bats*** with the RPMS. You get more energy return at the location that provides the most spin (which would result in a much slower ball at that point on a stock frame), and you have more inertia. It's a very very useful thing, and allowed me to I would estimate nearly double my spin out put compared to my old racquets.
If you look at the power maps from TWU you'll see that it isn't based solely on the stiffness of the frame, but all measures of the racquet, including the actual node locations, and weight distribution. They just use clever language to omit twist weight, swing weight and recoil weight.
Furthermore, most players as they develop actually hit in the various lengths of the frame for various effects. A lot of people aren't aware, but it's especially common with better players. This change makes striking close to the tip go from a low powered "bad choice" to a very effective choice, and when we talk about improving strokes, it's something that needs to be considered. Players (myself included) anecdotally/subconciously learn that going up there yields little power, and not much spin. And that's not a good thing.
The serve is a unique topic, because I've found with almost all players I work with, there becomes a point where certain swingweights become un-weildy and take more adjustment. Some players can jump right over in an hour, or less, some take a week or two, and some just hit a brick wall. That's all unique to the individual. That being said it's true that the swing weight boosts a lot less on the serve, and that you can serve big with a relatively "light" racquet. However, you still get more dwell time on the serve which means more power. Not a huge amount, but none the less more power on the serve. And again, the best servers in the world serve at the tip, where they have weight, and have a higher node location. So they do technically benefit from it. Just like the phys tech and tennis (I'm quite sure in one of the flex locations) explain you get a pretty sizable energy return boost with stiffer racquets on the serve, when serving from the tip. And that means a real world return on ball speed. Is it 50mph? No. But a free 3-4mph is, free. Throw in a powerful stringbed, with more dwell time, more inertia, higher node locations, and you will have a boost in your serve. Is it worth changing your setup all together for? Not for everyone, but considering you get boosts everywhere else, it's nice for sure.
We've already through and through established that at low velocities the higher SW is very important, and one place where it shines (in my experience above all), is the return of serve. Going from 320 to 350 gave me so much more command over big serves, especially kick serves, and those big flat ones out wide. It was a night and day difference especially with the increased stability.
But I digress. The importance of going to a higher swing weight is beyond just that it can help you handle pace, and create it. As a player I worked with a very good coach for many years. I stagnated (unfortunately). I hit a limit where my strokes were not getting any better. My pace cap was more than I needed, but my spin was limited. Spin was there, but unless I had a lot of pace to work with, it just was not enough. Then I changed to higher specs and the floodgates opened. I was able to do things on court I had been trying to do for so long. More importantly, I had to almost re-learn the sport. (with low sw) I could get away against big hitters with an overly long take back, and wasn't getting punished at all against regular players for taking the ball late. It helped bad habits linger, like relying on a heavy neutral stance on my forehand all the time. Which really put a damper on me learning better footwork/recovery techniques. You simply cannot separate the technique from the equipment and say one is more important than the other.
That's a big cornerstone why I've taken to such a blind crusade to push people to change their equipment. Not just because I improved, but because suddenly all these technique tips that I had learned from Pro's and all the money/time I spent on coaching, got unlocked with a FIVE MINUTE change. It opened up what I could do on the court, and changed the way I played. Suddenly I couldn't' get away with staying neutral on bigger heavier shots. I couldn't simply muscle the ball. If you want your players to get better, a higher weight racquet
can be a great catalyst. Since then I've worked with highschool players, and when I want to break some of their habits (usually on elongated reaching behind the back take backs) I give them the maxply. They hit the ball in a shot or two then just struggle. Then sit them down and show them how to abbreviate the take back. It speaks a lot more loudly because then suddenly it's the only way the get to the ball on time, versus their 11 ounce thing.
The consensus has been repeated by many sources; use the highest swing weight you can. It makes for a great cornerstone to re-evaluate your game, and help you learn to play better. And I stand by that, and so far with my time online I've had more than just a few people be very thankful for the changes I encouraged them to make, and that it did change their game. Not all of them were sub 5.0 either.
Im excited for our future debates. You put up a tough fight
