I have a 1998 and I have 2 transd. in the hull. I placed mine just aft of the bilge pmp. tried to find alevel place but is hard to find a place that is level. I removed the plastic discharge hose from bilge pump and caught plastic tie wire holding bilge pmp in place and moved it out of the way. Sandpapered a area bigger than transducer to clean it good then spread a tube of Lowrance transducer epoxy on spot. Stuck transducer in place and held it for several minutes till epoxy started to harden(tested with toothpick) than let set till next day and was good to go.
Also mine does not read on plane and I don't know if its from speed or the fact that the water I'm usually running on is over 100 ft. Hope this long response helps.