Dang!! This is almost a year old.

So, Don, how did it all work out? Did you go with straight argon?

In my learning experience, we were taught the following: straight argon for general TIG work, and a helium mix for some special stuff like heavy aluminum, if you wanted; argon-co2 mix on MIG, except for some special cases. I think it has to do with the composition of the filler metal, and the characteristics of, and the way the arc reacts with the base metal and the filler.