why not just do it on the command line of the shortcut launching wow?

main:
[code:1]"<path>\maximizer.exe" --display=1 --margin=0,1,0,0[/code:1]

assuming 1280x1024
clone 1:
[code:1]"<path>\maximizer.exe" --display=2 --margin=0,512,0,598[/code:1]

clone 1:
[code:1]"<path>\maximizer.exe" --display=2 --margin=512,0,0,598[/code:1]

this will create 2x slightly scaled (res / 1.172) 800x600 (682 x 512) windows they are scaled so you can fit them tiled vertically

This is what I used to use.

if you have 1600x1200 then you can use native resolution and the margins parameter should look like [code:1]--margins=0,600,0,800[/code:1]

with the --margin command remember the numbers represent the space to leave outside the display window: top,bottom, left, right