Just an FYI - I was getting an error when trying to create swimlanes.  
 

message: Invalid shape: 'swimlane' for reason: sum of swim lane widths must equal total width of swim lane objectThis error doesn’t seem to be impacted by the width though.  I can change the entire swimlane object to be half the size of the sum of the swim lanes and it’s not affected.  What does make this error come in and out is the height of the swimlane object.  If the height is less than the sum of the widths, the error comes into play.

            "id": "swimlane",
            "type": "swimLanes",
            "boundingBox": {
              "x": 140,
              "y": 200,
              "w": 560,  
              "h": 860

I’ve played around with this for a while - changing the “w” from 560 to 960 to 2000 doesn’t make a difference.  Changing the “h” from 960 to 860 will cause the error.  Just so happens that the three swimlanes in the model are 320 in width.  This doesn’t make sense for validation, so I’m assuming it’s incorrectly checking the “h” value instead of the “w”.  

Could be incorrect, but I thought I’d leave it here.