[CA11] RV-100 Placement on Fish/Ski Transom

I have 2006 Ranger Reata 180 with a Yam 150 and the placement choices are not the greatest, looking for some guidance to start off with to try. I have watched videos and read hundreds of blogs of where to place and unfortunately an 1 1/2 hour from the lake to play with it. I have seen this transducer screwed to the top of the step in front of the motor which doesn't make sense to everything I have read by Raymarine and other manufacturers. I have made 3 spots in attached photo where in numerical order where it could go, my steps are shallow and I have a curvature going starboard that would make this mount really difficult. If it is always submerged will that hurt anything? Top speed is 50mph. I am also wondering if the plastic stern savers are holding up for this large transducer? Thanks in advance for any assistance/guidance.

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