Thanks for the information. No, I haven't had the opportunity to see these jackets in person or try them on. If you are familiar with the Alpine Light, I have a question about the fit. My intention is to use it for spring, fall, and summer high altitude camping, and my idea is that I will wear it directly over my base layer, so I want a fairly snug fit. I am a small, slender guy - 5'6", 125 lbs. - so I really need a jacket that is not designed to be worn over other layers. I have a Montbell Extremely Light jacket, size small, and that fits perfectly, but I read one comment in a thread that suggested that the Alpine Light may be sized bigger. Do you know anything about that?
With respect to the Helium, I also ordered it in a size small, but may end up having to exchange it if it fits too snugly. The wonderfully informative Mr. Nisley indicates that some compression will not affect warmth, and since the Alpine Light is mostly for camp use, restriction on movement is not a big deal, but I will just have to try it on and see. Anyhow, thanks again for the information.