Bob, the distinction between layering while in camp and layering at a rest stop is quite useful. Thank you. ” Could we wear those (synthetic jackets) while hiking under my backpack straps and maybe rain shell and also expect them to keep us warm while in camp?” If we extend the distinction between layering in camp/layering at a rest stop/layering while hiking, it does seem that in cold weather we inherently need an extra layer for rest stops and while in camp.
And thank you, Paul, for your detailed reply. Regarding sizing, I had to purchase and return several wind shells before I finally got one that would fit over my down puffy. I think it is worth it, though, as the puffy is much warmer with the wind shell over it, and the XL Houdini is still quite comfortable when used without the puffy.
In general I found the article quite good. It has considerably diminished my desire for an expensive and short-lived synthetic puffy.

