Ignoring base of base class

I have UI classes like this:

class MyBaseForm : Form { ... }
class CustomerBaseForm : MyBaseForm { ... }
class WidgetCustomerForm : CustomerBaseForm { ... }

When I do this:

WidgetCustomerForm x = Isolate.Fake.Instance<WidgetCustomerForm>(Members.CallOriginal, ConstructorWillBe.Called, BaseConstructorWillBe.Ignored);

the base class ctors are not being called...unfortunately, I *WANT* the CustomerBaseForm.ctor and MyBaseForm.ctor to be called, but I don't want the Form.ctor to be called.

Is there any way to do this?