I'm happy to report that the new FW version corectly remembers which monitor you want as your primary in a dual monitor setup.
This issue on FW52.16 caused me to go back to the last Det release, as the 52.16 always kept wanting to make my 15" the primary monitor since it turns on an instant before my 19" when the machine boots up. Nothing I could do in Windows or in the nView set up could fix it in the 52.16 version (I must have spent an out trying to get it to work right). Now running dual monitors seems to work fine again, just like it always has on the older Dets. Glad they fixed it relatively quickly.