As I was posting last night I knew I had seen this issue addressed before. Finally remembered that I saw it in directions for making wide curtains. There's a discussion here ---
http://www.alternative-windows.com/matching-fabric.htm.
You might also consider piecing your fabric as shown here ---
http://sewing.about.com/od/beddingan...bedspread.htm. I think this is standard bedspread construction. I probably would not worry about matching these seams, I've seen bedspreads where the fabric does not match across these seams.