You could use xinerama, but I advise you (really really advise, not just suggest) to switch to the nvidia driver instead of nv, and use twinview instead of xinerama.
First, you need to install the correct driver for your video card.
The supported products list for the latest drivers is this:
You can find the exact model that you own by using this command as root:
lspci | grep -i vga
There might be a fedora-ish way to install the driver, so check the fedora docs, forums or whatever (hopefully a fedore user will step here as well). You first need to install the nvidia-driver, then you need to use an xorg.conf file suited for that and twinview. I put a link to mine here:
That should work, you need to fix or at least revise a couple of things:
1.- the modes on the Screen sections at the end of the file.
2.- the Device section, specially the lines about HorizSync and VertRefresh (reffer to the manuals for your monitors to set these to valid values, otherwise X might just not boot or do weird things). Also look at the MetaModes line on that section, and the TwinViewOrientation line.
As you might see, this config defaults to a layout with two monitors on 1600x1200 and 1024x768 respectively, and has a second layout for 1600x1200 monitor alone as well. I rarely use that second layout, but for some odd reason, some wine games do not detect the size correctly unless you have that second metamode with a NULL member.
But that's another story.