LightDM - Oct 2011 - passing geom and depth to VNC

Hi,

I tried to bring up tightvncserver on oneiric by enabling VNC in lightdm.conf.
lightdm brings up Xvnc and I am able to reach remote screen, but screen is
640x480x16.

Is there a way to pass depth and geom to Xvnc somehow?

Thanks,

Damjan