ajax told me that extra wide screens now work with the latest Fedora 9 binaries for X11. So I had to try it out and after some experimenting I got it to work. To save others the work here is what I did.

Hardware:

ATI FireGL V3600
2x Dell 3007FPW


I use the free driver, of course. No need for 3D here.

The old way to get a spanning desktop...