I string for a few friends and club members at a fairly cheap price as I like to experiment with different strings for myself . Strung an nvision with gosen polylon ice at 55 a couple of weeks ago the other day for a customer as they requested something very durable due to frequent string breakages when using polys Saw them yesterday at the club and one of the mains m5 has broken about 1/2" from head, the trouble is they expect me to restring it again for free as they claim to have only used it for half an hour or so and it shouldnt have broken. This is a young guy who hits pretty hard but he was adamant it broke after middling a mid pace shot. Couldn't see any clamp damage or nicks in the area of the break. Theyve been good customers in the past but I hate stringing full poly jobs and dont consider the strings or my technique to have been at fault. Any suggestions or guidelines as to determining what causes breakages at different parts of the frame? My understanding was a snapped string near the top of the frame is usually from a shank??