The transducer supplied with my new Hawkeye depth sounder requires a solid fiberglass hull with no wood, air or other voids in the installation position of the transducer. Is there such a position in my 1986, 27' standard rig catalina sloop? I've tried five locations just below the waterline but haven't been successful in finding a solid fiberglass spot that allows a transmission through to the transducer. Help!!!!