I am making a applique quilt that has hundreds of pieces of fabric machine appliqued on it and I haven't cut away the back from any of them. There is so much stitching, fusibles, etc. that I know the quilt will be stiffer than usual. this quilt will be used as a bedspread, not so much as a blanket to keep warm with. It is primarily an accessory to make the bedroom look good, not to feel good while sleeping under it. If your Sunbonnet Sue quilt is primarily for your granddaughter to snuggle under and keep warm, the extra fabric won't matter, but you won't want to quilt it heavily.