Stay stitch the edges by sewing 1/4" from the edge. Just a line of stitching but it really does help. If your edge has stretched a bit, use a larger stitch for the staystitching--almost a gathering type stitch. Measure thru the middle of the quilt and then divide that measurement into quarters. Divide the side of your top into quarters too, and pin them together. If there is quite a bit of difference, you can use that staystitching to gently gather and ease the edge of your quilt--kind of like sewing a set-in sleeve. I have also done this when my border has stretched and I needed to ease it into the binding.