It occurred to me that it would be a more refined installation without any regrets by employing a bushing (either nylon / aluminum) to eliminate any possibility of QD movement and thus should be included in the task. I chose aluminum. This would eliminate need for any thin nylon washers suggested the first time around and because the bushing is proud a few thousandths on each side, it will be the bearing surface for the backside of the QD cups. The bushing was gently tapped right in place, use a nylon head hammer to avoid marring your gun art.
Final appearance looks like something the factory would envy functionally and aesthetically.