Going back to an older version of RH is unlikely to help. Try a different
WM. I use openwindows, and it's worked fine for years, though all it does
is manage windows -- it doesn't have all that fancy cruft that KDE and
Gnome have (though I can run all KDE and Gnome apps).
I was, for a while, using gdm (and occasionally kdm) as my graphical login
screen, and it never had a problem with giving me two heads, once I had
logged in to a decent WM.

There are other WMs that work just as well, I THINK enlightenment will
allow two heads, I know blackbox does, there are others.