Thanks for the quick reply, the door without casing seems to do the trick for the appearance. Not sure about what it does to the underlying structure, but at the moment I need this more for general appearance than actual construction.
I've included the plan file with the original setup (divider wall in between the two rooms) and it has the gap if you want to take a look.
I also have no roof in this plan, but that's because I am still figuring out how to use the gable lines to model what my roof looks like. Gable for part of it, and flat over the back area of the house.
Thanks again for the help!
ceiling_gap.plan