I have done a bunch of dual screen stuff, and if I make my
stage the size your are describing, and play it back full screen -
it usually just works. The only hiccup can be if the monitors are
not set up in the system right net to each other or at different
resolutions. Make sure the stage location is set at 0,0 and it will
line up with the left corner and span as far as the stage is wide.