I know the avionics shop installed the aux GPS antenna under the panel, but I determined today that if the G5 boots up before the panel-mounted GPS (it's a CNX80), you get no track info. Since it's wired to the master switch, it comes on with the master. If I turn the G5 off, then start the engine and turn on the avionics master, THEN turn on the G5, I consistently get track info. I'm not sure if the install manual prescribes this setup or if the shop arbitrarily chose it on their own, but I don't consider it ideal.