This is not possible with Eyefiniti alone, the way eyefinity works the system sees it as a single monitor. You need to use a program like GridMove - DonationCoder.com , this application will allow you split the screen into sections or rather a grid. You can define the sections and the areas of the screen to which they snap to. Mind you you still will not be able to snap full screen in the defined area you will only be able to resize the window to the said grid area. This is what I use, and although not perfect, it works for me. I can upload my grid profile a bit later, and you can start using it. I'm at work right now.
Here is the Grid file for a 3 monitor Eyefinity setup: 3 Even and 2 on either side.grid - Google Drive
This splits the Eyefintity 3 monitor setup into 3 even parts. Then the two outer monitors can also be split into half.
Trigger areas for the halves are at the top, and for the entire screen anywhere else, I generally use the MMB to trigger.
Don't worry about the resolution, the grid files don't rely on it. This will work for any 3 display eyefinity resolution.