When I use .only() queryset method and there is more than one subclass I get DoesNotExist exception. It is raised in
obj = [getattr(obj, s) for s in self.subclasses if getattr(obj, s)] or [obj]
I believe this should be fixed by 6ab6da0 - I'll leave this open, though, since I haven't checked that to be sure, and I don't really consider deferred models "supported" until there's a test demonstrating that they work and preventing regressions. Pull request for that welcome.