I also tried the wet install using a rectangular walmart brand drybox. Worked great the first time but on the second trip the rough launch knocked around some items in my front hatch and the goop failed. No water = no finder that day.
I copied an idea from the darkhorse but mine uses the factory transom mount to attach the transducer to the sail mast on my revolution and all it does is sit flush to the hull. I add maybe a cup of water in the hull and voila. The zip ties are snug but not impossible to move and re-position. They can be swapped out in a second and it is difficult for anything to bang into it and cause it to shift. Worst case scenario, you slide forward and readjust. It picked up a signal instantaneously and never lost the bottom even through the 15 knot winds on Sunday PM. That area of the revo is a natural low spot and doesn't need much water to perform perfectly.
I really like that the transducer sits behind the mast and doesn't come into direct contact with other items in the front hatch.
I never had a good reading with two different goop installations.
I did not add the factory lock washers on the main bolt/cotter pin that holds the transducer to the transom mount so that gravity will naturally hold the transducer flush with the hull.
If you really want it permanent, buy a clamp that will fit on the other side of the sail mast and clamp it in position.