hmm. My guess would be 2 windows, side by side, 720x900. In the maximizer settings, just place a new region and put in this size, then lock them into place in the box. See if these settings look ok.

Edit: Though, you could also do 1 big window (900x900?) with a small window off to the side, but you wouldn't be able to really read the small window, you'd just be able to see whats going on.