Twinview setup has gotten so easy it works out of the box on Fedora Core 6. Just run the NVIDIA SETTINGS tool in the App menu of KDE or Gnome and you're set.
There is no longer any need to muck about in xorg.conf unless you want to enable the fancy wobbly desktop effects of compiz. I stuck the details of this on my site, www.thenerdshow.com
EDIT: I forgot to mention I'm using version 96.26 now. Get it.