Keep in mind that on these Newmars if the ceiling sags/droops where the ceiling air conditioner registers(small round and many of them) are mounted with/to the round "duct" that connects them to the linear ducts inside the ceiling, it will cause them to separate from these main ducts, and you will lose a whole lot of efficiency. The air conditioners will suck hot air inside the ceiling, and the cold output air will leak into inside the ceiling/roof cavity. IMO it's a design deficiency.
BTW any kind of small shade over the roof air conditioners will help noticeably. It did on mine, during Arizona summer.