I have a pair of ProKennex Ki15 PSE rackets. They are both 4 1/2 grip size. I have one strung with Black Magic/synthetic gut Titan and the other with Spin-X/ Gosen micro. Since I strung them up I have prefered the Black Magic strung frame. I am not a string breaker. I have gradually noticed that I am not hitting my serves in as much and my topspin forehands are not spinning as much and are going long. I have hit less with the Spin-X frame and have started hitting better with it. Last week I played doubles and was trying out a Ki5 that was strung with synthetic gut. I don't typically care for syn gut alone. I had been playing poorly with my Ki15 stick and decided to try the Ki5 since nothing was working. All of the sudden my serves improved and so did my forehand. The Ki5 was a 4 3/8 which made me think that it was the grip size. I just hit me that maybe it is the strings. I have not kept track of the hours on the stick, but I have been playing with it for 3 months 2 to 3 times a week. I am playing better with the Spin-X also, but not as good as the Ki5. It has quite a few hours on it too. What do you guys think?