This is cool! An interesting experiment.

I think a quick shadow does a lot to give the divider some heft and alleviate concerns about visual ambiguity between foreground and background page.

It would look something like http://cl.ly/image/2N3B2V2d2L3W (pardon the wonky #ss_topPage). It can be done in CSS (+ two empty divs, uh) with small effort. To me it feels like the most usable skeuomorphic hint you could drop.