dear X wizards: under gentoo, I have two Samsung UXGA DVI monitors,
running side-by-side with twinview and xinerama. the video card is a
GeForce 6600 GT with two dvi outputs. I am using the latest nvidia-glx
driver (7174)

I have learned that two monitors are a bad idea, because many windows
like to open up smack around the center bezel. very annoying. so, I
would like to fix it by making one of my windows not 1600x1200, but a
virtual 3200x1200. (I believe kde desktops don't do it, because the X
server does not believe that we have a span.) if possible, I would
want to have one of my displays essentially scroll as the mouse hits
the edge. In this case, X should believe my display area is 4800
pixels, and should open my windows by default on one half of my virtual
desktop on one of my two monitors---which is where I want them to open.

Just dropping a "Virtual 3200 1200" into the Display section alone
won't do this.

Has anyone done something like this?