This took about 1/2 hour to make. It allows a quick dis-assembly of motor and ability to install unique rubber band prop saver.

K&S 7/16 aluminum tube.
1/16 aluminum sheet stock
kevlar or similar thread
short 4-40 screw
CA
epoxy-micro balloons or your favorite light strong glue
scrap stick balsa filler

Tube needs to be drilled out slightly for nippy bearing housing shaft (Nippy uses metric sizes). I tapped a small piece of aluminum sheet for the 4-40 bolt, wrapped it tightly with the kevlar to the tube front, and CA'd in place with kicker

Then epoxied some scrap balsa inside the rear portion of the tube, and drilled it down the center to match Jeff's carbon tube.

Remove some foam to clear the aluminum tube assembly, and clean up the carbon tube so it will slide on, then smear epoxy and filler to glue in place. You can certainly use less epoxy and filler than I did. I was using 5 minute on two airplanes and didn't have time to clean the extra off.

I actually dind't glue the balsa to the tube (in case I needed to change the mount)