This may sound counter-intuitive at first, but if you leave 3 inches extra on the backing, then when you are done quilting, you will likely be able to get some strips wide enough to cut off and use as binding strips. so, instead of leaving 2 inches extra wide on the backing and then throwing out the 1.5 inches (or whatever) of scraps that are leftover, you could use that "waste" to your advantage. you would have fewer binding strips able to be cut and prepped ahead of time, but in the end, I think you would come out with enough....