On which operating system are you, first?
If you're on Windows XP, don't think there is a way, if you select the full screen one, it will get on top of everything else, including the reduced one.
Maybe something could be done with reduced-opacity windows, dunno.
You could only use the reduced one if it's on top of the full-screen window...afaik
just thought of this, if it was possible to modify priorities, you could make the reduced one always be on top, just like the windows task manager does...