Sleeping Bag Nesting

For winter camping, there are two schools of thought for how to combine multiple sleeping bags.  Well, probably more, but if you look to use two less-expensive bags to keep warm in winter instead of buying one very expensive bag, you can either nest the two sleeping bags (put one inside the other), or layer them (sleep in one, then just lay the other on top of you, like a blanket).

The major points are:

• Nesting - seems most obvious to try this, and it works well - but if you surround yourself with another sleeping bag, the 2nd layer of bag compressed beneath your body weight doesn't help as much, since all insulation is most effective when it maintains its loft.  
• Layering - theoretically, this should work better, because both added layers are kept on top of you, with full loft.  You should get added insulation that way.  This would be best, if you already have a good system for keeping you sufficiently insulated from the cold ground.  

So, I studiously kept to the layered system for several years, but finally I had to concede to reality:  I tend to move at night when camping.  Thus, the top layer gets shifted around and ends up not covering me as I'd intended.  Because I move around, the nesting works better for me, because I can't lose the extra layers or move out from under them.  But, your mileage may vary.

Thoughts from others on this topic:

• http://www.andy-kirkpatrick.com/articles/view/double_up
• http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=10415

This is just a brief explanation of a few finer points related to my winter camping equipment post.  If you somehow arrived here directly from somewhere else, go read the full post here:  http://newmexicocamping.blogspot.com/2014/12/winter-camping-gear.html