Thank you both for your replies!
Welcome to Epic. I sense that you're a better skier than he is. Based on that assumption, which could be wrong, there is at least one question that needs answering. What are his goals in skiing? Does he want to ultimately ski bumps, trees, powder or does he only want to ski groomers? The answer to that will have some bearing on the type of ski he should demo. And congratulations for him going to a boot fitter. And where in Montana do you ski?
Yes, I'm a better skier - somewhere around a high intermediate. Comfortable on all blues and easier blacks but I tend to stick to groomers as well. I'll have to ask him on what his goals are, though I think more immediate is progressing to skiing blue runs comfortably, maybe stay on groomers more this season. I figure this ski will be one that he can improve his skills on, and when he gets to a point where he wants to ski bumps or trees, etc., he'll either replace or add another ski that's better suited. And I forgot to update my account! I'm no longer in MT (though I used to ski at Showdown and Great Divide). I'm now in the Bay Area and skiing in Tahoe :)
Pretty darned good guesswork on your part. No matter what his aspirations are, a wider ski will not have him shredding the gnar automatically. My sense is that he needs a lot of time on task, some proper guidance, plenty of patience and a pair of skis that is good for what he can do now as opposed to something he may be able to do later.
A good choice for him would be something like a Blizzard Magnum 8.0 CA. This is a little higher level than what he needs today but won't kick his azzzzz when he goofs up. The beauty of this ski or others in this category (if he gets the right one) is that later on when he can shred the gnar, he can buy a ski suited for that but he'll still have a great choice for no-new-snow times.
Size will depend to some extent upon what he's accustomed to. A 172 is a safe choice for now but a 179 might be a little better in the long term.
Sierra Jim, we may be visiting you at Start Haus sometime this season when he gets serious about boots. For our upcoming trip he's renting skis and boots but I know he plans to invest in boots at some point. The rental guy put him on 165s for this trip, which is really short! Then again, when I skied with a girl friend (who is 5'8", 140), she was on 146s for her rental. How is the Rossi S80? An older ski (a couple of years old I think, model-wise) but I saw one he can try in a 170. I've skied the S80W and found it to be comfortable.