Thanks for the reply Robert. Here's a few pics. BLUE circle location is the middle lowest point on the rear transom. With the engines trimmed all the way down like they are in the picture, there's maybe 3-3.5" of clearance space between the transom and front of engines. Positives are that it's a flat surface and seems like it would work. Negatives could be is this location deep enough in the water - maybe not. I don't need readings at speed with the humminbird, just good side scanning. My glassed in Furuno transducer does quite well at speed. Another negative is I may have to trim the engines up to use sidescan?
Now the RED circle location is definitely deep enough and has no obstruction from side to side, but will the drain plug sticking out 3/4" below this location impact the sidescan readings if it is mounted there? A negative is this location is not perfectly flat and has a slight curve to it.
Surely someone has a sidescan on a similar boat hull? Contender, Seavee, and Seacraft owners cannot all be ignorant to Humminbird Sidescans!!!!