Middle finger will probably have the transducer in the air when you are on plane.
Actually... I'd make a temporary clamp-on mount so I could test assorted locations and find where I could have the transducer in water while on plane, giving good depth reading, plus NOT create a huge rooster tail kicking water back over the transom.
Ayuh,.... What's the bottom of the hull look like at the transom,..??
on a fiberglass hull, it can be mounted inside the boat with no loss of accuracy. And you'll still see fish that aren't there :lol: just kidding about the fish!