Since it doesn't have a stepped transom that I can see on their website, you have a couple of choices.
1. Attach the MEGA SI transducer at the bottom of the hull so it can give you on-plane depth readings. Center it between hull strakes to lessen cavitation from hull features.
2. BUT if you fish in timber/stumps, you may want to sacrifice a cheaper transducer to the wood gods and have the MEGA SI transducer about 12" above the hull bottom near the center line and add a XNT 9 20 transducer with Transducer Shield and Saver Springback bracket aligned with the hull bottom for full time 2D/Depth.
Connect the two transducers to the display with the 9 M SIDBY cable.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1