There's enough stiffness that it won't jibe in light winds, but enough stretch so that if it is blowing over 15, it will come around nice and slowly.

Part of the reason is, it is not attached mid boom. Rather just aft of the vang. So, there isn't much movement required to allow the jibe to happen. And of course, with the leverage on it at that point, the line will give long before the boom does. I have no worries of a broken boom, having used this set up for 15+ yrs. It works very well and behaves exactly as I want it to.

And all it took was $15 and an understanding of the forces at work. Well $30, really. I'm due for a new line. Last time I used it one of the strands popped on a jibe.