Thanks for your input on the reverse barbed needles! I'm glad to learn that they are useful for you!
I doubt that the merino breaks more when using these needles, but your point about using them with a coarser fiber is a good one! Merino is so fine that would be difficult to get the same results as one can get with regular rooting. Coarser fiber would be far more visible so the results would also be more impressive as seen in the photos of your work on your blog! (thanks for sharing the link