We are attempting to raise the ceiling in our condo bathroom. There’s a rigid duct over the vanity that is going to be turned into a soffit (if all goes well), however I was wondering if anyone had any suggestions on making the soffit as compact as possible. I know next to nothing about HVAC, but when I took out the vent cover there appears to be about 4” between the actual duct and the ceiling drywall - is there some way to make the vent collar (my terminology is likely completely off) shorter or just flush with the duct? Or maybe have the vent placed not to the bottom but the side of the soffit like in our adjoining area? How complex/expensive is something like this?