I demoed the Babolat PST from TW and like the control and flexibility of this racuqet. However I feel that it lacks some power in serves, and it's generally harder to get backhand slices right. I need to mention that the string on this racquet is a bit worn out, so it's hard for me to judge whether it's the racquet or the string. Can someone comment? If the racquet is a bit underpowered, can it be compensated by stringing at a lower tension? Thanks very much.