Don't think the si Transducer will work very well when mounted in-hull. I would call H'bird customer service and ask before doing it. Seems like your hull might interfere with the beam lobes and give you some funky response on your imaging unit.
Looking at your setup again, there is that strake right in front of your transducer. You probably have some really messy water right there.
I know a lot of people (me included) use a separate shoot-through hull transducer solely for the purpose of bottom reading while on plane. This allows you some extra freedom in mounting your si transducer - it only needs to work when you are off plane. I lose bottom on mine pretty much as soon as I plane out, which is where I rely on my in-hull just for a depth reading.
Here's a pic of mine - it has since been moved up just a tad bit and leveled out. If I move it two inches to the right the strake makes it a lot worse. This is the best spot on my hull, you have more room to work with below the bottom of your jack-plate. (You can see the Starboard mounting plate - I have a lot of flexibility if I want to move the 'ducer around.)
My in-hull transducer actually came as original equipment on the boat, and it is in the very back of the transom by the bilge. This gives it clean water underneath so it always has a good reading.