TwinView will compute the virtual desktop size by creating a bounding box using the largest mode listed in metamodes ... so if your metamode is :
Option "MetaModes" "1024x768,800x600; 800x600,800x600~
The bounding box is 2048x1536 ... (xinerama doesn't allow you to have a irregular bounding box) ... so the second head will use 800x600 but will pan across a 1024x768 area.
Even if you switch modes using <ctrl>+<alt>+<-> ... the desktop size don't change .. so both heads will pan across a 1024x768 area.
To solve it, you must run two X ... one in your TV and another in your CRT ... using the xnested or xggi xservers .....
Maybe you can find more info here: