I noticed that some people can hit extreme topspin and have that weird "click" sound in the strings. It's hard to describe but rather than a pop, it's like a click. You can emulate this sound by holding the racket with the frame facing the ground and bouncing the ball. While this is not especially useful but I am just interested. Btw, I do not have much of a problem hitting topspin on normal shots. I prefer to use an extreme sw grip close to western because I tend to grind points far behind the baseline.