Good idea to use the [same ordering](https://github.com/django-mptt/django-mptt/blob/0.5.5/mptt/managers.py#L181-L182) as the tree but trickier because of the variable attribute names specified in [MPTTOptions](https://github.com/django-mptt/django-mptt/blob/0.5.5/mptt/models.py#L14). Don't want to hard-code `ordering = ('tree_id', 'lft')` obviously. Thinking about this now...