The HB SI units (excluding ONIX) do not have a dedicated DI piezo pointing straight down ...

The DI views in the HB SI unit is a computer generated image from the "side pointing" SI piezoes ...basically the SI data rearranged in a DI image format ...

Therefore if any of your fishing methods needs Sonar data from straight down under the boat = a HB unit with dedicated DI technology would be of great benefit ...

Rickie