Hi guys,
You can do this. You just need to change the primary monitor before you launch the session of wow and it will render okay. When you change the primary monitor back to a monitor on your other gfx card the FPS will stay the same. As long as you don't 'cross the beams' so to speak and move the wow session from the monitor/vid card it was opened on to the other one, it'll stay at a normal, rendered fps.
I've got 3 monitors and 2x gtx 280's (H setup), my maximiser settings are set to open all 5 sessions on teh same monitor, but I need to change the primary monitor every time I open each wow session to their specific area. I have 2 on the left vertically stacked, monitor conencted to secondary vid card, 2 vertically stacked on the right monitor, connected to primary vid card, one in the centre, on the primary card too. As long as you change each monitor to the primary one in your display options you won't have a problem.
Edit - if my explanation about keyclone maximiser settings being set to the same window don't make sense I'll paste it from my config file when I get home. BTW someone should add this to the wiki probably, it caused me hell when I bought my system
-Frapp
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