Originally Posted by netllama
Also see the driver README's discussion of DynamicTwinview which explains this behavior and why its expected.
This hack is bad. Most people do not have two monitors. The default should be FALSE without user intervention in xorg.conf.
Monitor modes are one of the most critical settings in xorg.conf and playing with them like this is just extremely bad. Those who need fancy dual- or multi-monitor setups should be the ones who need to fiddle, not everyone else.