A nice little "button" you can make comes from a plastic clevis used on airplanes, etc. Just cut off the piece that has the hole in it, trim it to match the other side, so that it is round. Ream it out so that it will fit over the carbon tail shaft. I use fuel tubing against the tail rotor, then push this against the fuel tubing. It provides enough bite in the carbon fiber that you shouldn't have any more problems.