FlatsFokker,
As Newkid4si stated, Greg volunteers his time here when he can. There are many qualified people here who could answer your question as well, but since you directed it to Greg, no one else chose to answer yet.
As far as your deadrise, the 14 deg would be best if you do not have a flat spot or a spot near the V that will let you shoot straight (or near straight) down. You can build up the epoxy under one side slightly to compensate, but just make sure you do not over mix it and get any air bubbles.
I think you would be just fine with the 14 deg and just mount it normal. The angle of the cone is great enough that you will still be getting most of the beam straight down.
If you could post some picts of your transom and a few shots inside the hull where you propose to mount the transducer, we may be able to give you a little more guidance.
Thanks,
Robert