I am currently using Topspin Cyber Flash 17 on my mains and Topspin Cyber Blue 17 on my crosses. The combination is wonderful; however, I break strings every 4-6 sets of doubles. I hit with heavy topspin. I have tried using regular synthetic gut on my crosses for more durability, but I lose a lot of pop. Any recommendations on a multifilament string to use as the crosses to have more pop/power? I ordered some Tecnifibre NRG2 17 to try but they have not arrived yet. Any other suggestions? I would like to stay with the Topspin CF 17 for my mains. Thanks.