Aspects of the present disclosure relate to determining a layout of a racetrack that forms part of an RF isolation structure of a packaged module and the resulting RF isolation structures. Locations of where the racetrack can be adjusted (for example, narrowed) and/or removed without significantly degrading the EMI performance of the RF isolation structure can be identified. In certain embodiments, a portion of the racetrack can be removed to create a break and/or a portion of the racetrack can be narrowed in a selected area.