Paul, regarding your question about mass families in hummingbird. I don't have a complete answer for you but a suggestion. One of the key concepts of Hummingbird is that it separates the Rhino issues from the Revit ones. You can manually edit the .csv file in order to see why Revit is failing to create the geometry. Generally when you see a message that Revit was "unable to create the geometry" it means that something was too small or logically impossible to make. The ModelBuilder program just passes the message back to you without attempting to determine why Revit failed. Try some really simple geometry that in the .csv file unti you can get it to work and then you can analyze what you are getting from the Rhino-Grasshopper side.