It is. In the options screen you can select a configuration, but you'll need to tweak/create a file yourself. The ones provided are really just examples. With your custom config selected, type in the combined resolution in the options screen (rather than selecting something from the dropdown menu).
The game then simply renders a window of the specified resolution, with the config determining borders and position for the main view and additional elements.
Keep in mind that the total area needs to be a square though. If you have those monitors side-by-side, you need to use the total width plus the maximum height. Makes for 3840x1200.
Also, make sure you align the displays at the bottom, or part of the menu is unusable in MP. Can do that by dragging the icons in the Windows resolution window.
In more detail:
http://forums.eagle.ru/showthread.ph...=multi+monitor