Creating a Custom Hierarchy with Designer SDK

I am trying to add a Custom Hierarchy to my generated Universe through the Designer SDK. I can create the Custom Hierarchy entry itself but the documentation I downloaded provides no details on the Dimensions class that contains the Objects making up the hierarchy. I have discovered by trial and error that there is an Add method that allows me to add into the collection with a string parameter for the name of what I am adding. That looks pretty (in Designer) but since it doesn't acually work (drill paths in Webi) then it's not a whole lot of use. Does anyone know how to correctly add to the Dimensions collection? Should I be using an Object as the parameter, in which case does it come from the appropriate Class collection or the Default Hierarchies Dimension collection?

I am using what I believe to be the most recent set of documentation downloaded from the website. My XI release level is 3.1 in case that matters.