Lay a straight edge along the bottom of the hull to get an idea of where the water flow will cross the the transducer. I run mine just deep enough to get a signal at speed without throwing any rooster tail. Good place to start then tweak it on the water.
Besides height of the 'ducer, pitch forward and aft can make a big difference. Keep in mind that the overall angle of the boat changes on plane. Getting that right is usually the hardest part for me.
Nice job of mounting. That stringer might be a problem?
"Human beings seldom think for themselves... For the most part, members of our species simply repeat what they are told and become upset if they are exposed to any different view. The characteristic human trait is not awareness but conformity... We are stubborn, self-destructive conformists. Any other view of our species is just a self-congratulatory delusion."