Windows 7 - triplehead2go & stretched custom/default login screen on windows 7 pro

So, I've got a th2g setup with three monitors running at 3840x1024 . And it's great. Except for the login screen. And not just because of the default login background. The tendency is for whatever image I use (custom or default) it gets stretched, and looks bad.

I've tried putting a custom background for the login screen at the 'native' resolution 3840x1024 in c:\Windows\system32\oobe\info\backgrounds and enabling custom backgrounds, but it still squishes the width down to whatever width/resolution/aspect ratio windows wants it to be. The height remains okay.

Does anyone know what the maximum width/resolution/aspect ratio is for the login screen? I can live with it not going across all monitors, just as long as it looks okay (i.e not stretched).

Also, it appears that the initial login max width/resolution/aspect ratio is different from the ctrl-alt-del screen and logoff: each stretches the image to different widths across the 3 monitors.

Thoughts?