We are still working through this. Since we are mirroring the display in the 6x00M and the external display, we believe this will force the internal display to the same resolution as the external display (or vice versa). This is likely to make one or the other display not look as good when forced to a mode that is not "natural." We'll know more in a few weeks when we get a chance to work through this part of the code in more detail. We're likely to provide some guidance after we've been through this exercise.