Crossfire for Single-boxing, Not for Multi-Boxing

Any good ideas/ways to quickly/easily swap between Crossfire enabled/disabled?

I have a monitor hooked up to each 6850 I have installed, however when I enable crossfire (to run single-box or other 3-d games), the 2nd monitor goes dark.

Is there a good solution to this? Or do I have to just manually hook the 2nd monitor up to the 1st video card and back depending on how I want to play?

Just have both hooked up to the first monitor and have isboxer (if that's what you're using) direct which GPU is going to run which client(s)

How do you do that? I know how to direct it to specific monitors and to specific CPU cores, but not specific GPUs.