A bridge mount across the recessed foot pedal tray seems the most popular and sturdy. Plus you probably won't be pitching and flipping directly forward.
At least a couple of companies make that mount type.
Precision Sonar Mount
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, 360, RC-1