I agree Cliff. Not knowing exactly what his mountain streams are like... it does complicate matters when trying make an accurate rod recommendation.
You're right, If there is any heavy, fast flowing, water you certainly don't want you fish to get in it... especially if he has any size to him. Then, its almost a given that you'll lose him. So, you need the power to keep him out of there. That's true for any size river or stream. Cliff, I think you've just helped me add a new paragraph to my "Perfect Small Stream Fly Rod" article.... thanks.
So, here we are again. What do I mean when I say, small (or mountain) stream? What does someone else mean when they say small stream? So, what is it? Is it a small stream, a spring creek or a narrow river? Perhaps it is a fast flowing and turbulent canyon stream? Are all of these really the same thing? All fly fishers are not on the same page here.
Look up “small stream” in the dictionary. What do you find? Nothing, right? There is no formal definition of this term. I know what I mean when I say “small stream”. But do you see in your mind the same thing that I see? Maybe, maybe not.
When Funnel30 spoke of a "mountain stream" I pictured in my mind a peaceful a small Canadian stream that is one that you can cast across easily just about anywhere on it, that you can wade, often cross in hip boots, and has most of its structure exposed to view. As you suggested, this may not be the type of stream he's referfing to at all. My Colorado streams are never fast flowing when I fish them. If I was trying to fish them in the heart of the runoff then I would likely select a heavier rod. Probably still wouldn't catch very much.
So yes... like I said, it seems to me that there are a lot of variables here. The great folks of this forum will be happy to assist with rod recommendations. But before we can even be close to accurate... we need to know as much about all of the factors you'll be facing. What size fish do you plan on catching? How far do you need to cast? What are the wind conditions on these waters? What size flies are you trying to cast? How can you best describe you mountain streams? etc... For some advice on a small stream rod, you might want to read "The Perfect Small Stream Fly Rod" at: Favorite number of rod pieces?