LightDM on two screens + rotation

[Lanoxx]

Hi,

is there a way to configure LightDM to run on two Screens? I have a 
rather uncommon setup here. I use two screens a 22" 1920x1080 and a 24" 
1920x1200, I have placed the 22" Screen left of the bigger one and 
rotated it 90 degrees, such that I use if for programming and get some 
more vertical screen realestate.

Using xrandr I have setup the screens properly in Gnome:

  xrandr --output DVI-0 --rotate left
  xrandr --output DVI-1 --right-of DVI-0

The problem is now, that when start the computer and try to login, 
lightdm does not know about my xrandr settings and shows the greeter on 
the rotated 22" screen, which makes it quite difficult to properly 
choose settings and enter the password. I always have to tilt my head.

Is there a way to tell lightdm or the unity greater about my setup?

I am using lightdm with the unity greeter on 12.10 and with the Gnome 
Fallback mode.

Regards
Lanoxx