puchfinnland

"How were you planning to cut the threads? By hand? I see your whole scheme as relying on having access to a lathe anyhow, so cutting spacers is no bid deal."

I have friends with access to cnc machines, this would be a moonlight job.

older freewheels have each cog threaded on.
the hg freewheel type they are splined, just like casettes

of all the choices on how to do this -narrowing the body,
by cutting new threads for the locking washer
and making some spacers
is the most simple and repeatable method of doing this
all the wearing parts are replacable and off the shelf then.