The TD on the motor is only for normal 83/200Hz sonar. I was thinking about something like this, though with Lowrance, but it was pointed out to me that DI/SI mounted to the TM is going to be all out of wack, it will be turning and such with the motor. Just do one unit with SI/DI, mount it on the dash, with the SI/DI mounted on the transome. Then you toss out markers or you can tell the TM to Spot-Lock the area and you could fish it off the rear of the boat. Then put a less expensive unit on the bow which can still show the images from the SI/DI unit. Sounded reasonable to me.