Anyone have any experience with this new string? The G.M. of Tecnifibre USA told me it's the replacement of TF's flagship string, their great 515, a soft string similar to their NRG2, but one that keeps its feel for weeks, and is very durable (for me, at least. I just bought TW's last batch, 10 sets). I just tried X-1 Biphase and it hurt my wrist alittle---I don't want to waste money on NRG2 again.... Thanks in advance.