Not over the wing keel!
I tried several locations: just behind the cooler location, in front of the port-a-potty in the bow, on the port side.
They all do work. The bow location gives more noise in the signal, but otherwise it is fine.
Most important to bring down to bare fiberglass and use thickened epoxy with no air bubbles trapped in it.
If you don't like the position,you can always pop the transducer off and move it to another location.