There are an easily way to change the position, size and order of the swimlane shapes in your dsl. To do that, you just have to create a partial class of the swimlane that you want to modify its boundary and then override its BoundRules property, like this:
Also you must create the BoundRules custom class and override the GetCompliantBounds method which returns the rectangle in which the swimlane will be painted. This method receives the shape and the proposed rectangle, with those values you can alter any of that as you wish.
Specifying the rectangle you be able to change the location X,Y and also the size of that swimlane.
Enjoy.