Finished job yesterday.
Have not used it yet to see if any good, but below the hull it is clear all the way forward and all around it.
It is really a nice near flush design, very little sticks out and it's a gradual transition. Airmar did a excellent job.
I'll measure it off tonight to give you the placement.
It's sitting just rear of the bilge bulkhead on the starboard side. Had to cut an opening in the oil tank floor, then make a new larger flat floor for the second oil tank to go side by side with one on the port side.
Besides the Xducer, I extended the starboard battery platform twice as long, which is the 2nd reason had to move oil tank.
6 inch C clamp worked like a champ on the big nut, used it with foot off. I used the usual 12 inch channellocks to hold body from rotating while torquing nut. BoatLife Life Caulk against hull, GE silicone II to line spacer, and some LifeCaulk on nut threaded and set screw threads.
Another tip: there are two neoprene washers, the one on top under the big nut was squeezing out when torquing nut. All I did was coat it with light silicone (GE Silicone II) both sides and nut surface and she stayed in place. I read over at THT, members would get rid of washer, I can see why. But the silicone allowed the nut to slide evenly on the neoprene otherwise it will bunch and push out under little torque.
Last note, don't forget, the arrow pointing at keel on X ducer head means just that, don't make the arrow parallel to keel.