Multi-monitor spanning on OSX

This question has been asked multiple times, but it hasn't been asked recently (ie: using recent OS, version of Unity) and there never seems to be a definitive answer anyway.

Is it possible to have a single OSX standalone app span multiple monitors "fullscreen" in OSX 10.9/Unity 4.3?

It is possible in other apps once you deselect "Displays have separate Spaces" in System Preferences > Mission Control, but I can't seem to get it to work with a Unity standalone build

Things I have tried:

1. Unchecked "Capture Single Screen" in Resolution and Presentations

2. Start app in Windowed mode, then set resolution with Screen.SetResolution(3840, 1080, false) , then enter fullscreen mode with Screen.fullScreen =true;

3. I was encouraged to see that a Unity app will span multiple displays in windowed mode, which seems to be enough for Windows when combined with the -popupwindow option. The problem is that it doesn't seem possible to hide the menu bar and title bar on OSX, nor to position the window such that it is hidden. There don't seem to be any command line options like there are for Windows that would allow frameless window.

I very much appreciate any tips!