Hmmm....
Reading through the [link|ftp://ftp.matrox.com/pub/mga/archive/linux/2002/lnx200notes.txt|release notes], I see configuration information and specific mention of the G200. You might want to take another look.
I'm certainly no expert, but it looks like you should be able to get something going. For example this excerpt.....
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
DualHead and G200 MMS support
=============================
To add DualHead support for the G400/G450/G550-based graphics
hardware and multi-display support for G200 MMS products, the
following sections of the "XF86Config" file need to be modified:
- "Device" section
- "Screen" section
- "ServerLayout" section
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
.... would indicate to me that it's possible. YMMV
