Does anyone use twinview to run two monitors at different resolutions?

I've got two monitors one on top of the other with the lower 
resolutioned one on top.  The one on top (lower resolution) has a dead 
area where the window manager/X thinks exists but doesn't show. 
Sometimes the window manager will put windows there that I can't see.

I'm not sure where the problem is because different window managers 
treat it differently, although the dead space exists in all of them.

In fvwm, for example, if I maximize a window that is predominately in 
the lower resolutioned monitor it will make that window take up the
entire visible area not including the dead space.  Yet, fvwm does load 
windows in the dead space sometimes and I can drag my cursor into it.

Fluxbox maximizes windows to the entire desktop, both monitors, which is 
annoying but that's another issue, including the dead space.

xorg.conf is attached.

aristotle ~ # emerge -p fvwm

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild   R   ] x11-wm/fvwm-2.5.18-r1  USE="gtk nls perl png readline 
truetype xinerama -bidi -debug -imlib -rplay -stroke -tk" 0 kB

Total: 1 package (1 reinstall), Size of downloads: 0 kB

aristotle ~ # emerge -p fluxbox

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild   R   ] x11-wm/fluxbox-0.9.15.1-r2  USE="nls truetype xinerama 
-disableslit -disabletoolbar -gnome -imlib -kde" 0 kB

Total: 1 package (1 reinstall), Size of downloads: 0 kB