Abstract: Display backing components for head-mounted devices (HMDs) are described that reduce eddy currents in magnetic fields generated by a coil. A HMD may include a coil that is used to generate a magnetic field that may be used to track position of other devices with respect to the HMD. Display backing components, used to provide rigidity, are modified with holes or other gaps to interrupt the path of the eddy currents and reduce the interference with the magnetic field, thus improving the power efficiency of the coil and of the HMD. These modifications may be formed by casting, drilling, cutting or otherwise perforating the display backing during manufacture.