Here is the bracket that Lowrance has for a flush mount in the bottom of your boat that I used. I got excellent readings installing it between the ribs of a 1648 g3 jon. And got excellent bottom readings at 26 mph. It worked for me. Don’t know if they make a bracket for your transducer like this, but it won’t be hard to fashion. The transducers 6 screws fit this flush mount.
StructureScan 3D & Totalscan Skimmer Flush Mount | Accessory | Lowrance USA