I know what you are saying Chris. Still I have a Bayliner 175 that came with transom mounted xducer and it works great. I know I would sometimes sail the Mac at high speeds using the motor (that's why I got an M). So, why assume the trepidation of cutting holes into a perfectly good hull if I can simply mount it in the transom (and just be careful not to knock it off).
Another idea I'm considering is somehow link it to the ballast valve handle. This way, when valve is closed, xducer is in the water. When I open the valve to drain, xducer is raised. I will never operate without ballast, so in operation xducer will always be in water. More ambitious, but doable.