In my RV-8A, the VP-X is mounted on an avionics shelf that spans the width of the cockpit behind the panel. It can be accessed from either the front of the panel (by removing the right EFIS,) or from behind the panel through an access panel in the front baggage compartment. All of my avionics are mounted behind the panel, excepting the GPS20A, and there's plenty of room for additional radios or a GNS if I require one in the future.