I've tried installing 10.6.8 using newfoundglory's method, or close to it, but I'm having a problem with cursors and the second monitor connection. I can tell exactly what the problem is: the system has problems counting connected displays and separating the two ports.
I have one monitor connected via the DVI (and the included adapter) to the HDMI port. When I go to System Preferences->Displays, and click on the Arrangement tab, I see two identical displays. So, the system thinks there are two copies of the same display. The cursor problems make sense: the system is sending cursor updates to both displays, so the cursor can get confused. intel HD graphics 3000, like all graphics chips, has a hardware cursor, so the system just updates some registers with the cursor position and image as necessary.
If you plug and unplug displays on the two ports, part of the system recognizes the connections and disconnections, but I can't find a way to delete the phantom extra display. I can get the spanned second display to show. Mirroring doesn't help. It seems like there should be a way to do this. I've looked at IORegistryExplorer and booted into UEFI with rEFIt, but I haven't found anything.
So, for those who've successfully installed 10.6, can you verify that you don't have the phantom display? If not, then there must be some difference from what I've done.
I have:
Mac Mini 2011 2.3, Firmware update applied.