I would not say that the transducer is sitting too low. It may need to be lowered if you are wanting high-speed depth readings off of it. You can try slightly lowering the back end of the transducer down (only a few degrees) to help with that as well.

Got a screen snapshot of what the Si sonar looks like? I’m thinking that the Lowrance transducer just to the right of the HDSi transducer will block some of the right Si sonar and may cause a repeated Si sonar return but would have to see a screen snapshot from the Si sonar to know for sure. Take several at different Si Range settings and please include one at a setting of 20 feet.