Fishfinders
Franklin,
Glad to hear you're working on those kinds of things, sounds like things are moving along for you, and that's great.
A friend in Chicago has a Hummingbird fishfinder on his C34, and hasn't bothered to go back to his depthsounder. He doesn't fish but likes the features.
Good Old Boat's newest magazine has an article on just that. Includes an in-hull transducer, no new holes in the boat.
If you do a search on fishfinders, I recall many earlier discussions on the topic. Sounds like a very good alternative. Largest challenge is to mount the head end unit so that it works for you in your cockpit.