I strung my Ti Radical OS with Vs Tonic+ Gut mains and ALU Power Feel 120 crosses, at 53/48 lbs, constant pull machine, with some prestretch on both. I have been playing with it for 3 weeks, it felt great, nice and firm. Yesterday I let a friend try it out, and within 4 strokes, a string broke at the grommet. Yikes! He may have framed it, I can't remember. I've strung natural gut quite a few times now, and never had this happen. I suppose it's a right of passage or a lesson to learn. The dangling string is the last main, it was tied off to another main with a double half-hitch. It seems like the string broke directly at the knot. Is it so simple that I'm pulling too hard when tying the knots? I use a starting clamp to grip the string and pull quite hard to "cinch up" the slack in the string. I will admit that I've been trying hard to eliminate slack and tension loss in the last mains (or last cross) to avoid that pathetic looking loose string. I have heard folks say they tie knots by hand, and I can't understand how that's sufficient. I have stuck with the double-half hitch because it's easy and I saw no reason to change, maybe it's time to learn other knots. Although, I suspect it was the cinching force that caused this incident. There goes $20-$30 of string. I've got another stick I'm playing with these days so I'm not too upset. Better this happened now, on my own racket. Any advice or criticism is welcome. I repent!