Olddog, CA glue (super glue) bonds to amsteel quite nicely. You could try the Turk's head on the carbon fiber shaft and saturate it with CA. Spray a little accelerant to cure it. That should make for a nice hard, fixed stopper. You might even be able to get away just glueing a clove hitch, wrapping the tails around before applying the CA.
Another idea that addresses the thin wall of the carbon fiber...find two sizes that telescope together. That would increase the wall thickness between the turk's heads. I'm guessing there is some lateral stress on the bar in the middle. It would be simmilar to Red's original idea with the PVC, just lighter and more streamlined.
I've been following this thread with interest since the start. Now I've got to try it for myself. Darn it, ANOTHER project to spend time on happily.