Joe,
I searched for answers to this exact question for months a year or two ago. The answer from Lowrance is that the DSI does not have 2D sonar so you cannot use it with a 2D sonar transducer. DSI is a downscan only (although yes I’m aware that playing with the display on that unit allows it to “look” like 2D sonar, it is not).
You could mount up the DSI transducer on an “arm” and put the whole contraption on a genz box. By muddy does this with a very old unit that doesn’t have an ice ducer and he fishes just fine.
I really liked my DSI but sold it due to problems I had with a newer Lowrance an their customer service or lack of in that instance. That is a phenomenal bow unit IMO.