No, I'm not smarter than a fifth grader - oops - no I'm not smarter than you! LOL
I'm just going to toss out an idea. Hand baste 1/8 inch seam. That way you can keep checking alignment. If it's where you want it, then do your 1/4" seam. Then remove your hand basting.
Another thought, just trim off a couple of inches and make it look like the rest of it where the corners don't meet?
My DMIL gave us a cheater cloth quilt a while back. The center was the width of the fabric, then she divided the fabric in half length wise and added to each side of the center using piping to divide the fabric. Then she took it to a long arm quilter and had a meandering stitch over all of it. It's really pretty.