Decoupling design of one-degree-of-freedom controllers is treated for the generalised plant model within the H-2 framework. The class of all realisable closed loop transfer matrices is parametrised under a mild assumption on non-unity feedback sensors. A set of compact assumptions is presented to guarantee the existence of the optimal H-2 controller. Together with the optimal one, the class of all H-2 controllers that yield finite H-2 cost is obtained. The optimal closed transfer matrix and its associated controller are shown to be strictly proper under the reasonable order assumptions on the generalised plant.