please refer to this link: http://www.badmintoncentral.com/forums/showthread.php/32158-RSL-Series-Racquets/page107
I just bought an x5 last Friday and i only had the chance to use it yesterday. Since i'm a beginner i really don't have much to say but i think it's best used tension 27. I find it easy to use unlike my previous racket voltric 80. That's all.