is dual-head (or even xinerama) supported yet?

Is there any documentation out there for Xvesa, Xmga etc? 
according to the -help (switch)  there seams support for xinerama but I cant 
find any further information how to set it up.


Off course I would be very glad to use both screens, if anybody has dual-head 
setup maybe he can post the switches for Xvesa (or X....) on the list. I am 
sure lots of people would be very thankful 


I have a matrox g550 + 2x17"
should this card be supported by Xmga? Currently I get:

Fatal Server error!
no matching cards found



Thanks all!