Roma Rear Seat Q — Big Enough for a Cat?

Very random question for any Roma owners on here. I might have the opportunity to borrow a Roma for a couple days for a trip, but I need to be able to bring my cat with me (long story). He rides in a backpack-sized carrier, but we also bring along his litterbox, which is around the size of a large carry-on suitcase.

Does anyone know if there'd be enough room to put him and his litterbox in the back seats, my significant other (who's six feet tall) and myself (I'm six foot four) in the front, and a couple of soft clothing bags in the trunk?