Marie, the wide backings are wonderful and you'll have no seams. Keepsake Quilting has several choices you can order from their catalog. Judy in Torrance

Marie, depending on your own personal measurements, the BOM will finish to approximately 85" square. That means that two lengths of fabric (I would get 5 yards) will be enough for the backing IF the fabric measures more than 44" wide, but you won't have much extra on the sides. :shock:
That will allow for a seam down the middle, and trimming off the selvage edges, but not much for matching the pattern at the seam.
You might want to consider making a pieced back and making it large enough to be more generous around the edges!
A huge sawtooth star on the back would be really cool!

This may be thinking too far ahead, however, I am wondering about the backing fabric already. How much do we need? How would you piece the back?
Marie