Here's the description of the hardware setup, the issues experienced and the test cases.

Harwdware setup:

Dual monitor setup with 30" LCD display (resolution: 250x1600) and Cintiq-21UX 21" display (resolution: 1600x1200)configured in xinerama with twin-view enabled configured either with the 30" above the Cintiq or the Cintiq to the right-of or left-of the 30"

 * The Cintiq is connected as the primary display

Issues:
- Since the virtual desktop is 2560x2800 pixels, a dead-zone is created which is 1200x960 pixels (when the 30" is above the cintiq) and 1600x400 pixels (when the 30" is to the left or right
 of the cintiq). The windows manager or a user can lose a window in this region, since the window manager is not constrained to the visible display area.
 This also makes tracking an issue when using a Cintiq pen for application which need the window manager to pass it coordinate information and becomes
  worse when pressure sensitivity data is also sent to the Cintiq.

Test cases:
- configure xorg.conf as included in the attached xorg file.
- open multiple windows (with width smaller than the deadspace i.e.: width less that 480 pixels, hight less than 400 pixels) until all the visible desktop area is filled. Windows shouldn't vanish into the deadspace
- open single window on the 30" display. Resize to 400x400 pixels or smaller, drag it to the right edge of the 30" and using the mouse drag the windows straight down.
 The windows shouldn't go into the deadspace
- On the cintiq, open a window of 400x400 pixels, drag it to the right edge using the mouse, drag it up until it gets to the 30", the window should warp and follow the bottom edge of the 30" where the deadzone overlap is.