i need a soft upper stringbed as i break strings at the 6th cross top down. therefore all my encounters (have been only 3!) with poly/co-poly crosses have been a disaster, no matter how low i have gone on the poly (down to 18kg with 22kg on the multi mains - never played gut mains / poly-crosses!). i am on one hand quite confident that the zx is a good cross string for poly mains, but due to the raving reviews on gut mains / poly crosses, i'm rather inclined to give this a go with what i have at hand, i mean gut mains and zx crosses, than trying poly mains and zx crosses for now. it is very likely that i will order another set and then i will surely try out poly mains / zx crosses. i'm also waiting for the zx pro to become available, i think the thinner diameter would be even better as a cross. i just wonder what the durability will turn out to be. with poly mains i'm currently at around 6hitting hours, the last stringtest i did with gamma poly z 1.25 was the absolute disaster, not only due to the poor qualities of the string but also due to the fact that the mains broke in about 2.5hrs, which is absolutely unacceptable.