I just got my racquet strung with a different stringer. When I got my racquet back, I noticed there was excessive vibration, and an abnormal noise when making contact with the ball. I just thought it was a bad string, quite suprised because SPPP is good.. Later, I noticed that the mains, when crossing the bottom two crosses, went over both. I'm not a stringing expert, but it's supposed to alternate every time, right? Is it different for a 16x20 racquet or something? (It is a Wilson KPro Tour, if it matters).