when I put my zippers in cloths, like a back of a dress, I would baste the seam closed, press it open from the wrong side. get out your tape, Scott magic or clear is good. tape your zipper over the opening. so, the seam is facing up, and the zipper is facing down. run the zipper down the seam carefully and tape in place. a 7" should take 3-4 pieces to keep it tape basted. start at the top stitch down. cross over the bottom, and go straight up. then take off tape, and remove basting. you did iT!!