Jim, we run our SI transducer on a 6 foot trolling motor shaft with the Johnny Ray adapter. We dont have the Tm on the shaft, just the transducer. We can keep the ducer down far enough to keep surface air or cavitation out of the beam. this is of course at trolling speed. (usually abut 1.5 mph) If we were to hit a below the surface object the shaft and transducer flip up out of the way. SI is sensitive to a lot of influence so any thing we can do to make it work is worth the effort. Great job on your modification. Chuck