I recently got some 1.9mm Tech Line from DIY Gear Supply, and was having a hard time getting a prusik knot to hold on it. I was originally trying to get a prusik of 1.9mm Tech Line to hold on itself, but it wouldn't really hold very well.
What I eventually did was take 3 strands out of a length of 550 cord, braided them together, and tied them with a double fisherman's. Voila! Holds pretty well, but will slip under really heavy load. I'm using it on a 14' cat cut tarp as an "over" ridgeline. It didn't slip from ~5-10mph wind and me pulling/tugging on the tarp. However, if I pull directly on the biner clipped to the prusik it will give. We have some 15-25+mph winds and rain coming up soon so we'll see how it does then.
I'm testing out all my new gear so hopefully I made everything correctly and set it all up correctly
Hope the Tech Line prusik info helps someone else.