The black and white polka dots won.
I trimmed down the first grey border to 1" (from 3"), added a 1" stripe border then finished off with a 5" black and white polka dot border. The quilt top is now 60" x 90".
I've now sandwiched it and have begun quilting. I've chosen a time consuming 1" all over grid... on point to the main design. It will take a fair bit of work to get it all done, but I still have 20 days until the end of June!