Cal T2 sonar transducer location

Jun 18, 2019
1
Jenson Cal T2 Huntsville Al
Has anyone mounted an in-hull sonar transducer in an early 70's Cal-T2 or Cal-2-27?
I am new to sonar so I have a few questions. I've gone bow to stern looking for a good location to glue the transducer down.it seems it's always off by 4-6 feet. In 12 feet of water it reads 8.2 feet slide the boat out of the slip to 16 feet of water and it reads 10.1 feet.
My boat is a 71 Cal-T2 so I know the hull is not honeycombed so it's either going through a secondary floor or the fact that it's not glued down means it's not making a solid enough contact against the hull.
Does anyone know if the floor under the cockpit in the bilge is against the water or is there another sub floor beneath?