My wife and I use ONE Western Mountaineering Megalite. However, she made a 9oz sweetie pie from a nylon blanket. The zippered nylon blanket looks like a triangle with zippers running up the long side. We share the foot box. The Megalite lies on both of us. Most of the down is on her side <img src="/forums/images/graemlins/smile.gif" alt="" />. When it gets too warm, we flip the bag over.
There are other methods for two; other posters will respond.