I just installed a new HB 899 ci hd si unit at the helm of my crappie attack vessel. I installed my HB 698 ci hd si up front so now I can use my Navionics HotMaps Premium map card up front. To avoid having to take the sd card out of one unit and xfer to the other I thought that I might interface the two with an Ethernet cable. HB says that it does not xfer Map info, just position. I would like to interface the two because I could use the sd xducer installed on transom, I'm using the ipilot xducer up front. Any info would be greatly appreciated.