Turn off mirror display on startup on Elementary OS

I’m running Elementary OS Freya Beta 2 with dual displays. I added some xrandr commands to run at startup so the monitor I want is the primary monitor and that the dock starts on the right monitor. Now whenever I restart the machine, the display mirrors. Is there a way to force the display not to mirror?

I can go into Settings>Display and turn off “mirror display” but I don’t want to do that every time I restart. Where I can I permanently modify those settings?

Here are the things I’ve tried:

• xrandr: There’s nothing I can see in there that forces not mirrored displays
• xorg.conf: As far as I can tell I don’t have an xorg.conf file and cannot automatically generate one. If the answer is to create one from scratch I can do that. I just don’t know what to put in it.
• drivers: I tried using the proprietary ATI drivers but that cause a lot of graphical issues, right now I’m just working with the xorg drivers