I'm trying to take advantage of BuddyPress 1.7's new theme independence to effectively create different pages and instances of the Activity Stream with different themes.

I can use HeadSpace (an options plugin) to change the theme for a specific page and one "Template" under Page Attributes is BuddyPress - Activity Directory.

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I use both in conjunction (as shown above), but setting HeadSpace to use a child theme returns the BuddyPress Default Theme (but correctly returning another instance of the Activity Stream, proving that it can be done) and trying to use a normal WordPress theme (i.e. Twenty Twelve) returns an HTTP 500 error.

Is this possible, and how?