Ok, from Argile (or I suppose any other external program where one would create morphs):

In Poser:

• Export only head (not eyes) as Morph Target (I was selecting the eyes too, and exporting with options other than "as morph target" selected.
• Edit in Argile.  Export as mentioned http://www.n-sided.com/images/tutoriaux/tut_ds_en.pdf
• Import morph target in poser with head selected (object, load morph target)

Going to try it now with the M4 characters.

BTW, so far I find Argile a lot easier to use and to create the changes to a body/head I intend as compared to Blacksmith 3D.