Stephen, I have been satisfied with an 11mm static line made by Roca, in Spain, for moderate load speedlining. It stretches less than 2% at 80 kg, and has a tensile strength of around 40 kN. I've had it several years...don't remember the model name. It is solid black, like an assault line, and is stiff...hard to set knots. 200 feet of it weighs about 12 lbs.
It has more stretch than some of the specialty fibers, no doubt, but meets most of my needs.
It worked well for handled ascenders before I converted it to rigging use.