OK, I do garments (and sew for DG all the time - just a you I know how to make work for myself - lol). You can go to Joann's and pick up the new fancy zippers (they look like lace, very sweet), and sew it on "TOP" of the back. You don't need a zipper foot and it just looks like a design on the back of the dress (very simple). This way you can keep your seam allowances (without shorting yourself), with all of the big designers using zippers that show on the back of dresses your DG will be in style and you can keep your sanity too.