OK...I ripped out the old top and bottom borders, remeasured (at the center as I've been instructed to do in all my previous endeavors), and re-attached new borders.....without mitering. Still dealing with a rippled effect as you can see from photos. I am NOT doing another do-over; so I carefully gathered up the ripples and pinned a fake seam ever so often. My plan is to quilt over the "seams". I haven't decided whether to hand-stitch the opening down before or after quilting. This baby is not coming off the rollers again, so sleeping on that decision tonight. D-a-r-n, d-a-r-n, d-a-r-n those bias seams!