If you have an aluminum boat you may not have the issues that fiberglass owners do. My Skeeter has a dual level hull and the Helix transducer (w/side scan) doesn't get low enough in the water to keep reading while on plane. Many guys are going with two transducers as a fix, and getting the Y-cable to support two; one on plane and one for going at slower speeds. That's what I did.
The smaller transducer is below the transom, underneath by the pumps & drain. This one reads depths at faster speeds. The Side Scan transducer is mounted on the transom and reads everything at slower speeds because it remains in the water deep enough to get the readings. Check out a couple YouTube videos with a search for Helix transducer and see how they mount for fiberglass applications.
I hope to get out on the water next week for the first time and see how this new setup works.