While there is some fish-finder signal loss, shoot-through or in-hull transducers (available in both 600- and 1,000-watt versions) often prove an acceptable compromise for trailer issues.
Also, no holes need to be drilled. The installation is less difficult than in other methods and involves securing the face of the transducer to the inside of the boat. They come in a wide range of angles, allowing you to mount them on the angle of a V-hull. But they can only be used with solid fiberglass boats.
Tip: Test a selected area inside the boat by placing the transducer inside a water-filled plastic bag. Wet both the outside of the bag and the inside of the hull and hold the transducer as tight to the hull as possible. If your sounder registers down to the depth you fish, you are safe to install the transducer at this spot.