The NEXEL Alumina-Bora-Silica fibers are by far superior to the fiberglass wick, but you need to remember that those are braided ceramic sleeving and teh size measurements are I.D, not O.D. The fiberglass wick we are using will actually fit INSIDE of the XC4-116 sleeve. With a wall thickness of .074" it will be about 1/8" OD and will be far too big to use without somehow eliminating the internal hole.
I do know for a fact that they do not burn except at much higher temps that we typically generate at our coils and the the wicking performance of that material is excellent. We'd need to find some in a 1/16" braided cord or rope though. It may still work....I have not tried it in iAtty yet.
It all depends on how well it will handle stretching to eliminate it's internal cavity. I know it has good tensile strength, but I also know that once cut it frays out to separate fibers very easily and quickly.