Its my understanding you must have an in hull transducer to get bottom reading while on plane, all external tranducers I've ever had have lost bottom signal while on plane but down/side imaging tranducer cannot but in hull. If you've got an old lowrance transducer in the hull you can connect it to other brand units via a NMEA backbone you just may have to buy a cable and some T's like these http://texasfishingforum.com/forums/ubbt...AR#Post11349567 As far as switching between two tranducers on one unit not sure what all that involves but I know some of the bassmaster guys do this, could also just have two units at the console one for each transducer.

I still have the in hull transducer mounted in the back of my boat when I had my humminbird. I'm probably just going to mount my humminbird unit to my console and reconnect it to my in hull transducer using it to read depth while on plane.

I don't worry about it when I am on plane, I am usually using the GPS and watching the map. I slow down when I get close to what I want to scan.