I am moving this subject from rackets to strings. My 17 son who has a big cut on the ball has decided to use this racquet after demoing. What string have you guys been matching with for this stick? Previously he was playing with the Zone 7.1 with BB ALU at 55 lbs. Over the last year he grew a couple of inches to 6'1" and added 20 lbs of muscle as he has been lifting and with his old set-up, he couldn't keep the ball on the court! Your suggestions are appreciated.