It appears that Autodesk Revit does not use the D-Cubed 2D Geometric Constraint Solver (AutoCAD and Inventor do) for parametrically defined sketches. Revit parametric modeling s*cks. We always have to create reference planes and then lock edges to these planes. And then Revit claims it's "overconstrained" when it clearly isn't. We cannot link parameters directly to a dimension constraint (again, Inventor can). Why not something like Inventor's iLogic system? Can we dream?