I have an iMac running at 1920x1080 resolution with a second monitor connected that is running 1920x1200 resolution.
Whenever I enable "Mirror Displays", OS X Yosemite 10.10.4 (14E46) will always set the resolution of both the second monitor and iMac screen to 1920x1200. It always sets the "Optimize for" drop down menu (under display preferences) to the external monitor.
Is it possible to default both the iMac and the second monitor to 1920x1080 when I enable display mirroring? Essentially, I want the "Optimize for" option to default to the iMac screen.