Originally Posted by pumpkinpatchquilter
I have never done it except for maybe practice sandwiches. Depending on what you're making you might be able to make it work but I agree you'll lose a little bit of your quilt that way. If you run out of fabric for your backing you can always piece your back. Add a border to it or literally, piece the entire backing. ;)
Piecing the back is a great idea, but I wouldn't add a border to it without cutting down the piece you already have by a few inches on all sides.
Otherwise, there's the chance that the border seam will fall at the same place as your quilt top edge and will lead to extra bulk when you put on your binding. Plus you might just get a sliver of the other fabric showing on the back (which would look weird).