For the electrical connections, would it be sensible to help get the polarity right by, for example, saying the left rail shall be connected to a plug on a wire and the right rail connected to a fixed socket. This allows modules to be connected without any additional wires, and the dangling plug can be put in the socket for transport/storage.
Also, should the coupler height be specified? On my rolling stock I've fitted MicroTrains couplers at a slightly lower height than they specify, using a Dapol gauge.