[Hampshire] Window managers and TwinView

I have a TwinView (two monitor) setup that currently runs IceWM. I run
with six virtual desktops. I'm looking for a window manager that will
automatically put all windows that appear on one screen (the right-hand
one) on all desktops. ie, if I drag a window from the left to the right
screen, it will then appear on all desktops.

Must be doable, but doable in a relatively easy way? I'm happy to consider
other WMs. How a window that spans both screens is handled isn't important.

Any ideas?

Keith