[Answered ]-Django – Override Default Manager in Admin – InheritanceManager

I had the same issue, and found hacks to it one way or another. But it never felt clean.
I ended up using django-polymorphic…

When we store models that inherit from a Project model…

Project.objects.create(topic="Department Party")
ArtProject.objects.create(topic="Painting with Tim", artist="T. Turner")
ResearchProject.objects.create(topic="Swallow Aerodynamics", supervisor="Dr. Winter")

…and want to retrieve all our projects, the subclassed models are returned!

Project.objects.all()
[ <Project: id 1, topic "Department Party">,
<ArtProject: id 2, topic "Painting with Tim", artist "T. Turner">,
<ResearchProject: id 3, topic "Swallow Aerodynamics", supervisor "Dr. Winter"> ]

Using vanilla Django, we get the base class objects, which is rarely what we wanted:

Project.objects.all()
[ <Project: id 1, topic "Department Party">,
<Project: id 2, topic "Painting with Tim">,
<Project: id 3, topic "Swallow Aerodynamics"> ]

Hope that helps!