Lion's full screen and secondary windows

In my document based apps each document has a main window and can have =
several secondary windows. The main windows should be allowed to go full =
screen. However, once in full screen, it should be possible to still see =
the secondary windows that belong to the same document. So in the new =
Lion full screen feature, that uses a separate space for the full screen =
window, how can I make the secondary windows move to the space reserved =
for the main full screen window?=20

I know about NSWindowCollectionBehaviorFullScreenAuxiliary, but that =
only says something about the type of window, not which full screen =
window (and therefore space) they should belong to. I.e., I only want =
the secondary windows of that belong to the /same/ document to appear on =
that space. AFAIK there is still no API for the space that a window =
appears on.

thanks,
Christiaan