Thanks for all the helpful information here.

I've started making some of these for my guylines, tried the locked and the unlocked. Not sure there is much benefit of the locked for a Prussik on a guyling.

Using 14" of 2.2 Zing-It with 1.75" buries, is that enough bury?

Prussik is a locked loop, and the other one is open.

The larger needle is a #13 Birch Tapestry needle, and the other one I don't know the size, but it is fine for passing the bury. I use a pair of craft pliers to pull the needle through, couldn't do that with my fingers - not enough grip.