Step 17 – Sand the outside of the motor tube to rough up the surface for the epoxy to stick to.
Step 18 – Mark the motor tube 6 1/8” and 1/2” from one end of the motor tube. Epoxy two of the three centering rings on each of the marks. IMPORTANT: make sure the motor tube is clean of epoxy from the centering ring that is 6 1/8” from the end for the remaining 15 or so inches of the motor tube because the fin roots will need a clean surface to attach to. At this point it is a good idea to test fit the retainer because it is much easier to sand the motor tube now rather than later.
I had not yet purchased the retainer, so I had to stop here.