It does seem odd to pair the high end MFD with a lower end transducer.
We have a 2018 Cutwater 28. Our transducer is an Chirp style in-hull made by Airmar. It's installed up front in our boat, under the floor as you step into the v-berth. So sounds like it's easier to get at than yours.
However, the problem is that we don't have all the beautiful features that the 7612 XSV is capable of, too bad! It requires a higher level transducer, and likely a through hull installation. I had one recommendation - to install 2 transducers, one on either side of the keel, which would give full coverage beneath the boat. According to this recommendation, having one installed on one side - the keel will block some of the 'cone', and hence - having 2 (one on either side) - the cones will overlap giving full coverage.
So this is if you really want the full bells and whistles. I do kind of want that - especially with the great technology of the 7612 XSV. If anyone hasn't seen what these things can do, take a trip down to the local WestMarine or equivalent, and see the demos, it's amazing how the sonar technology has advanced. Having the plotter without the correspondingly capable transducer - - it's kind of like having a beautiful 4K TV screen, but only with some local low-resolution public access channels. It just doesn't make sense.