You're welcome. This one is actually my second portable sonar setup. My first was a Bottom Line 2D finder in a plastic box powered by a Dewalt 12V drill battery. I still use it when I am in my belly-boat because it is much smaller and I don't need the GPS in the BB.
Yup - just let trail out back where it is out of the way.
I like my HB Helix 5 DI GPS. The GPS feature sold it for me, as I had been using my Garmin Hand-held unit which lacks most of the features the HB has. I considered the SI version, but SI can be hard to read especially on such a small screen. I find great detail running DI on one side of the screen and 2D on the other. The two modes compliment each other and give a very graphic picture of what's on the bottom. The DI works best while moving and the 2D when sitting still.
Sometime I wish I had a bigger screen making it easier to see. In the jon boat I sit it on the seat besides me so it is fairly close to me. However in the canoe it sits on the floor and that puts the screen kind of far away. I have been known to pick it up and get it close to my face while using it in the canoe.
Good luck on your install and let me (us) how you made out.