Setting Structural Materials in Compound Families

I have created several floor types with the wrong material.
I would like to set the material automatically. All my floor types containing the EXT prefix in the family name should have the same material. In Layer [1]

I use the Clockwork Node FamilyType.SetCompoundLayerMaterial but that doen’t work.
I think I need a SystemFamily.SetCompoundLayerMaterial but I’m not sure.
I have a 1.x version of dynamo.

Thanks in advance.