Yesterday I was supposed to playtest X-Yellow VS X-Dual Silver Lite but eneded up playing the X-Yellow 99 for 2 hour long. The string on X-Dual Silver Lite was dead anyway.
Set-Up: The Yellow was freshly strung with Solinco Tour Bite at 55 lbs, so the pop and bite were there. It has +0g butt cap installed with no weight slide at all.
Ground Stroke: I exchanged groundstroke with my hitting partners with low to high speed ball. The X-Yellow 99 seems to be best at low to medium speed ball while my favorite Blue 99 is good for fast & heavy groundstroke. The light & thin frame cut thru the air very quickly and produce uniquely solid feel like no other. It's very easy to hit angle shots from corner to corner at various speed levels. However I need to adjust my grip. Normally, I hold the Blue 99 and other heavier racquets towards the end of handle, but for Yellow I grab the handle approx 1/4" higher up. It is a very effective way to play the X-Yellow 99, at least for me. Actually, I copied this practice from one good junior player
http://www.youtube.com/watch?v=C1MJuFcDBMk. (I asked him to test the X-Yellow 99 after he won U16 and U18 titles on the same day. So he looks a bit tired.)
Power: it doesn't have so much power when hitting flat honestly. In fact, I don't think the X-Yellow 99 is good for flat hitters. The best way to generate power from Yellow is to hit half-flat/half-spin with faster swing, and most importantly weight transfer. Not only swinging my arm, but I had to move a whole body to hit the ball and get power out of the X-Yellow 99. The lighter weight and 3pts HL really help me master that kind of shot in a natural way. Even though the racquet is very light but the X-Yellow 99 can block/return heavy ball very well.
Spin: This is the hightlight. I have good result in hitting spin at knee level and waist level as effective as from Babolat Aero Pro Drive GT, but I got much more ball feel/bite from the Yellow. The ball seems to sink into the string bed longer than APD, so I can feel more ball bite. I don't get this kind of solid feel from other spin-oriented racquets like Babolat AeroPro Drive GT, Head Extreme MP, or Prince EXO3 Tour. The closest one is Head Speed Pro, but it's way too heavier and sluggish.
Volley/Slice: Some users commented about volley issue (stability) but I found no problem with that. It doesn't volley very sweet like Blue 94 or Wilson Pro Staff, but it's good enough. Because it's a light racquet, good footwork and weight transfer skills are required for punching deep volley. Forehand and backhand slices were sharp and much easier to hit than with heavy racquets.
Summary: The yellow 99 is a fun racquet to play and at the same time can be a serious weapon for all-court aggressive players. It's good for pure spin and best for half-flat/half spin. If you have Novak's swing style, you may like Yellow. The solid core feel makes this racquet very special in comparison to other spin-oriented hollow racquets in market today. In addition, it's one of the best control-oriented frame in a light racquet category I have tried. If you expect powerful winner shots, this is not a racquet for you (Go for Platinum 99). But if you have all-court game and love hitting the winners with extreme angles, the X-Yellow 99 can be the alternative to your current racquets. Those who use Wilson KTour 95, BLX Tour 95, or Babolat Aero Pro Drive and look for a faster racquet should try Donnay X-Yellow 99.
Soon I will be testing X-White, and X-Dual Silver Lite and will update you guys again.