Unless the customer wants to remove the charms and spacers, you
could take the end off of the chain, put on the charms and spacers,
then resolder the endpiece. The result is a necklace with everything
kept on the chain.
If the charms and spacers are to be removable, why not cut through
the back of the spacers and spread them enough to slip over the chain
end. If you are concerned that the spacers will deform, solder a
decorative trim over the opening and you’ll have double-sided
Without seeing exactly what’s going on, I hope this makes sense,
Judy in Kansas, where we’ll see sub-zero temps tonight and winds that
make it even colder!!