Seeing how you brought it up, I am not getting the furled leader out of Fluoro idea. Sure fluorcarbon sinks but not like a brick by any means. Soak a thread leader and it will sink fantastic for nymphs and streamers. Plus there is Kevlar. Fluorocarbon being as expensive as it is and the fact I think Vanish is junk (my choice), I don't get it. Just use more tippet, use fluoro tippet. If fish see my leader, they are seeing too much, but some fish just dont care. People want stealth, I think it is more in the delivery and the tippet, not the leader and flyline, however both will make it possible to deliver that fly the way and the where needed.