Per Bob Noble:
Seems like a good thing to ask at the www.kokatat.com web site.

Sometimes I miss the obvious... Thanks.

They actually did have a couple of one-page instructions on the process. Sounds
like they use the same general approach I used in that they lay parts on a flat
surface instead of inserting a cylindrical object into the neck.

Without any pictures, it's a tough call, but the essential feature of their
approach seems tb the use of a flat disc that the outer collar can be folded
under.

--
PeteCresswell