When I'm trying to match seams and the seam allowances aren't pressed in opposite directions or if seam allowances are bulky, I sometimes pin and baste a few stitches, just where the seams will hopefully match, check to be sure I like it, then stitch the whole seam with the normal stitch length. If it's not right, it's a lot easier to remove a few basting stitches than the whole row of normal stitching.