If you have enough length to spare in the piece of backing fabric, you can cut the whole piece from top corner to opposite bottom corner on a diagonal. Obviously, accuracy is required! Then you can slide the pieces, one up and one down, until you have the backing width you need. At this point, you sew the cut pieces back together. You will then have two small triangles to cut off, one on top and one on the bottom, to square up your backing. If you are only lacking 2 inches, your triangles to be cut off should be small. Weezie