What is the standard/average string tension people use? I have the Yonex Isometric 300 and would like to string it with either the BG-65Ti or the BG-70 Pro. Which one would be a better choice? I'm just an average recreational level player, would 18lbs be good? Someone said that lower tension produces more power, but yet I've read so many people here string it at around 20-21lbs. Does high tension stringing also produce power? Thanks for all your input.