I'm currently attacking the coupled lines problem on two fronts.  Firstly, we're working on a microstrip coupled model, using the design equations (like every other microstrip model).  Second, I'm working on a 2D Method of Relaxation code to add to Mason.  This will be slower than the design equations, but initial tests show it isn't too bad. 

The 2D MOR code will be accessible through the math parser, specifically through several new functions.  Devices taking advantage of the new feature will be added using the same file format as the existing dynamic (primitive) components.  The changes should be available in the next couple weeks, should be considered "beta".