Zac,
Nice ride!
IMO the above cited location is the best spot. I can't tell from the photo but If there is a strake, step or separation strip that runs along the bottom to the transom.. put the transducer just inboard of that. If you put it outboad you could loose the signal during maneuvers. Inboard of the strake is a region of positive pressure. On the outboard side of the strake can be a turbulent location.
Good luck with everything.
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