I finished the cap in one piece on the CE mandrel as far as applying the CA glue, but not sanding. I took the measurement of the inside tube and marked it on the wood with the tip of a skew. ( I made two clean line cuts to equal the width of my parting kerf tool - 1/16 ) Just barely deep enough to cut through the CA finish but not so deep that I separated the pieces. I then sanded the CA and polished the piece. Then, very carefully, I separated the end cap piece - catching it in my hand so as to not damage it. I then put a piece of 320 grit sandpaper on a flat surface and lightly flat sand the cut edges of both pieces in a circular motion.
I then insert the piece in the end that normally comes with the kit (the piece the kit cap threads onto) and place the clip on the end. I mark the width of the clip on the rim of the cap and cut a little slot in both pieces with an exacto knife just deep enough for where the cap comes out. Then it's just all CA fitting from there.
I could do a little tutorial with photos if there is interest.
Martin