私の日本語はまだ下手だから英語でコメントします. I'm a long time hurricane 3 user. I have a lot of experience gluing Hurricane 3 rubber. If you stretch the rubber like what Yoshida-san did in this video, the result will be bad. Because first, the sponge is still hard and not flexible. When you stretch it, the sponge will be tightened, but because it's not flexible, the ball will just jump from the racket. You will lose a lot of control from the rubber, and it's difficult to generate a lot of spin. Also the pimples in the rubber are only stretched upward and not sideways. When you boost a rubber, not only the chemical will stretch the rubber, but it will also make the sponge more flexible too. Because of this, you will have more dwell time in the rubber and more trampoline effect, resulting in better control and you can produce higher spin. 悪い日本語のショートバーション。 私は長い間のキョウヒョウ neo 3 使ってる人です。この伸び方(stretch)はダメだとおもいます。なぜならスポンジがまだ硬くて flexible でわない。後、粒が上だけ伸させた。ボールが早いだけ、でも回転とコントロールがよわい。塗る(booster)の場合は chemical でスポンジが flexible になって、粒もちゃんと all directions に伸ばす!コントロールと回転が上がります!