Re: 4 monitors, two cards, twinview, center on monitor
If I interpret your posting correctly, then Gnome/compiz finally implements
multi-screen support so that you can run compiz with two separate cards
on four monitors (xinerama disabled)? In this case, it should be sufficient to
define two screens per cards rather than using twinview. This should supply
compiz with the correct screen information (check nvidia driver readme
"Chapter 15. Configuring Multiple X Screens on One Card" for details on
how to define separate screens).