I'm just reading this for the first time, and noticed in the rules that it's OK to buy fabric for backing. I wanted to share what I've started doing: I always have big pieces of fabric left over from each project that I sew together and use for the back. Sometimes it's just three fabrics in big sections (like a regular back would be sewn anyway) but sometimes I like to piece a few more. Sometimes I use fabric I bought for the quilt top, but ended up not liking it so I "get rid of it" on the back. If I use up scraps from the top, I figure in the future it COULD be used to repair a spot on the front. I've really been enjoying using up more fabric this way. I hope this is helpful for someone.