Though in a quick Google I can't find out what they mean by that snippet. But having one desktop manager managing multiple screens at least creates an architecture where what I want is possible.

I'll look around more later.

Thanks,
Ben

Update: I spent some time trying to find documentation and couldn't. Then I looked at their mailing list archive and everything that I found discussing dual head setups strongly suggests that their integrated multiscreen support boils down to stuff like, "When you maximize an application, it only should cover one screen." I will still join their mailing list and ask whether it can do what I want, but I'm not very hopeful.

Update 2: From responses on the mailing list, it is definitely not possible. :-(