I don't know that I would tell the world that I'd been ripping off the feds. Just sayin...
I've still got some 550 that I use as general utility cord, but when it's gone, I won't replace it. In addition to the stretch, it doesn't hold some knots reliably.
The stuff was developed for shroud lines on 'chutes...it's designed to stretch. since there's enough of it in the federal supply system to go to the moon and back several times, it gets used for just about everything, but that doesn't make it good, just available.