You could add more borders under the scallops. You could make and quilt out the borders. Then slip them under the scalloped edge about 1 inch above the highest point of the scallop, and sew on with your machine. Then on the top side, you could top stitch, or hand stitch the curved parts of the scallops to the new boder that it lies on top of. You would probably need to use a thin bat so that the area where the two parts are attached together doesn't get too thick or heavy.