I have only done one pieced back and it was not a problem. I had a fabric that I was in love with for the back of a quilt, but not enough for the whole backing. I cut the fabric in 10.5" squares and pieced with alternating solids. The 10.5" size is a suggestion on the Quiltville website. The quilt was a gift and the pieced backing was a hit with everyone. I am getting ready to do a similar back on a postage stamp quilt I just finished piecing. I went to JoAnn to find backing and was so disappointed in their stock and quality that I came home empty handed. Good luck. I know you have gotten a lot of great advice here.