My wet mount install cost was $14 for the 4" pvc threaded pipe end and 4" rubber cap. The rubber cap is 1/2 thick. I shaved the pvc piece to fit the left section of the hull next to the tackle area and marine gooped it in place.
The transducer was screwed into the rubber cap and the wire opening was sealed with marine goop.
After everything had dried completely I filled the new pvc well with 18 oz of water and slowly put the cap/transducer on the pvc pipe. Water spilled out a bit as the transducer went in. Tightened the SS clamp as was good to go.
This setup is +80% more sensitive than when I siliconed the transducer directly to the hull. I had my sensitivity setting on 18 and reduced it to 2.