Charles,
Firstly this is a theoretical discussion, and I have no interest in producing my own Argentium silver, of any variety. There may be people that like the discontinued alloy for whatever reason, and still want to use if for personal "non-commercial" use.
If just a a theoretical question it is not worth thinking about. If
you really want 970 then buy 940, pay the maker his license fees and
alloy it up to 970. It might not be an exact copy of the real stuff
but should be close, and you can sleep with a clear conscience
jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand