Comment 6 for bug 455378

I assume there is a setting in compiz to allow this. Prior to upgrade to 9.10 I was able to resize across monitors without special key strokes.
I can override the output settings in the general tab by changing the output to 2560x1024. However, clicking maximize on a window goes fullscreen across both monitors. Prior to upgrade, maximize would be limited to single monitor which is the preferable action.

A large majority of my compiz settings were reset during the upgrade so it's proven difficult to find the setting allowing this option back.