I've been considering upgrading my console Helix 8 G3N Mega DI unit to a SI unit. I really want to get better at finding (and potentially catching!) offshore bass and crappie this summer. Every tutorial I've seen (mostly from Fish The Moment on YouTube) has side-imaging as a critical component of finding success when offshore fishing.

Will side imaging work on my boat if I mount the transducer on my jackplate? Is it worth it to upgrade?

Yes, that is a typical installation, both the left SI and right SI need an unobstructed view to the sides. Just need a 2D transducer in the bilge for Depth/2D when on plane.
Transducer Shield and Saver makes mounts specifically for that application.

You cannot "upgrade" a DI unit to SI unit, you can replace it.

That's what I meant, purchasing an SI unit and doing something else with my DI unit.

Use the DI unit at the bow or beside the SI unit for mapping/GPS/Sonar/DI.

You would want to have full screen with Side Imaging since the display is so small.

I just bought a Helix 12 MDI for my bow and just networked it to my 1198SI at my console until I get a new trolling motor.

I was surprised to see great SI views on my Helix 12 MDI at my bow. I did not now know this was possible.

I already have a Helix 12 MSI at the bow and I like the size of screen for that when using it for 2D/DI/Waypoint (I use casting rings when fishing offshore). Instead of moving that to the console and putting the DI at the bow, I'm thinking of just selling my Helix 8 DI and buying a Helix 8 SI.

IMHO , side scan is one the top 4 technology advancements in fishing ( behind livescope and spot lock and gps)

I have had sidescan for many years , the first trip out , I found a big brushpile that we still catch fish on today.

The best advice I ever received about side scan was look at look at locations you know about ( rocks , timber , brushpiles) so you can recognize these
features when you see them elsewhere. Just yesterday , I found two new brushpiles moving from one known spot to another.

MO