just ordered a Helix 7 for the front of my boat. Humminbird wants sixty bucks to exchange transducers. They said you can by a bracket that will let you mount your transom mount to the trolling motor for 24 $. Any experience with this. My thought is buy the trolling motor transducer. I already spent 600 for helix and map card whats another sixty and I know it will work. Thoughts please?