I've been wondering how well side imaging works with the transducer off the side of the canoe? I know the placement and leveling has a big effect on getting good quality returns for this compared to the standard 2D transducers.
I'm planning to bring a Garmin 73sv UHD this year, but will be buying a new transducer for it. (So I don't need to pull one off my fishing boat) Trying to decide if the SI is worth it or will work for the extra expense and pack weight.

Side imaging can be a fantastic tool for use out of a canoe. It really excels in finding that offshore structure that fish love like rock piles, downed trees, steep breaks adjacent big flats, etc.

You're right though, if you don't have a good transducer mount that keeps the transducer level, you likely won't get accurate readings. I'd recommend a RAM mount system if you're serious about canoe fishing. Not cheap, but a fantastic portable and super durable system I've been using for years.

Side imaging transducers are twice the size and do suck up more battery life, however. As with all fishing gear in the BW/Quetico, there are always pros and cons to every setup. I decided not to go with Side Imaging to keep better battery life and less bulk/weight.

I'd just try it out on some nearby home waters first.

But yeah, SI would be a nice thing to have at any point, anywhere. You'll just need to have it in the water deep enough to clear the hull of the canoe to see to the other side. But yeah I like the ram mount option, I have one for my livescope pole and it works great.