I have tested the V1.3 PCB and it works. My previous observation regarding the +/- symbols was in error and they are in fact the right way around. My next task is to design a enclosure to 3D print. At the moment I have the board inside the cardboard box that my Pi came in. To optimise performance you should minimise temperature gradients on the board. The best way to do this is to enclose it, even in a cardboard box!