Solution
I think that the only way to do this is to use a Matrox TripleHead2go or similar. It will trick your computer into thinking that you have 1 really wide monitor (enough to split into 2 or 3 screens depending which model) then the TripleHead will split the image into the proper amount of screens making 1 image across 3 screens. It works with ANY application too.
I have a slightly different issue with my setup, how do I make the presenter screen go on screen 2 and the display onto screen #3... So that my iMac is NOT being used, just the other two screens. This is necessary for me because the two external monitors are sent to a stage monitor and the screen... Currently we are mirroring the iMac's screen to screen 2... but it makes everything flash during the transition.
Basically, can I specify which screen the presenter and presentation images are displayed to? (When using a 3 monitor setup)
Thanks