My large Bitterroot fits just like a large should. Not an athletic fit, not too baggy. The thing about the hood is, I don't see how it could fit over a helmet at all--it's not that roomy. I doubt that it was designed to be helmet compatible.
After Randy and I exchanged posts yesterday, I took my Bitterroot down to the basement war room, where I had good lighting and all my small tools. I checked out the elastic that rings the front of the hood. I found that I could probably carefully thread some thin cord through the opening at one end of the elastic (it's not sewn shut, but it's rather a tube that runs the length of the face opening), and add cord locks on each side where the cord leaves the tube. That would allow one to close the face opening dramatically. Then, if one is into it, sew a couple of velcro strips on the back of the hood to add that adjustability option. I won't do this myself, since I like the hood on mine just fine.
I adore my Bitterroot, and it's a steal at $150.
Edit--I want to also mention a few features that make this coat unique, vs. some of the other coats mentioned: it has a double zipper, the hand warmer pockets have zipper closures and are lined with a thin fleece (warm and comfy to the touch), and there is one zippered interior pocket that is large enough to hold a 1-liter Platypus. These features add a bit of weight, but they are worth it to me.