I am going to install a Zumo 665 in my 2012 RGU. Book says I need to plug into the front aux jack to hear the XM from the 665 or mod radio for external rear aux jack. But I am thinking that the radio is already wired to accept the HD XM radio. Has anyone added wires into the HK radio 35 pin connector or used the ultra overlay wiring kit (comes with the XM radio) or I have seen refernce to a 12 pin connector, to connect the 665 xm audio to the HK radios XM audio in, thus making the radio think there is an XM radio installed? Update I alos see an HD part number 70172-06 that implies it will connect, but will still need to know how to make the radio think the XM is plugged in. My guess is this is either +12V or a ground jumper within the XM radio to the XM connector.