Thank you for getting back to me. I did look at the swimlane example, but i was looking for an example without the header in the container. I was able to hide it, but when it's dragged and re-sized it reappears and doesn't seem to be calculating the dimensions correctly. I couldn't seem to find a property to hide and / or set the height of the header to 0.
You are right that there is no straightforward way to achieve the required behavior. However, there is a possible way to hide the header of the container shapes.
You can try extracting the default template of the RadDiagramContainerShape control. You can follow the steps described in this article.
For your convenience I extracted it along with all resources that it uses in the attached file. Once imported into your application you can try setting the Visibility property of the ContentPresenter called "NormalContent" to Collapsed.
Please give this approach a try and let me know if you need any further assistance.