Get a cheap flip-flop (if you have a kid steal one of theirs). Cut out a section in the general shape of the transducer, but about two inches larger in diameter. Then take the piece you just created and cut out a cavity in the same size and shape as the transducer (which should leave about a one-inch border around the cavity). The transducer should fit snuggly in this cavity. Use Marine Goop to glue the piece to the bottom of your kayak, making sure it is sealed to the bottom of the kayak so that the cavity will hold water without leaking. You now have your receiver for the transducer installed, just remember to put water in the cavity before you try to use the sonar. This will work fine in the center of the kayak hull even though it is not flat, and, you did not have to glue the transducer to the kayak. I did this three years ago on my yak and it still works perfectly.