Yes, that's what I did (because, obviously, the class being abstract is not the cause - works great in other scenarios):

Class Test.NewClass Extends %Persistent [ Abstract, NoExtent ]
{}

Class Test.NewClass1 Extends Test.NewClass
{}

I do know you don't inherit all from the secondary class, but I though the number of things I do inherit was more than just parameters, properties and methods. I take it queries, foreign keys, triggers, projections are out as well?