The RadDiagramContainerShape class is quite limited as a container because it has a header, resizes to fit the content and has fixed padding around the borders for the children. A simple base RadDiagramContainerShape that doesn't have a default style and doesn't impose any layout constraints on the children will be very useful to create custom containers to build nested shapes for UI design tools. Thanks Reason for Closing: Changing the class the RadDiagramContainerShape inherits from will be a breaking change we cannot afford. The mentioned customizations are possible via inheritance and custom styles.