location to install the WAX610Y

Installing the WAX610Y on a ranch style home. 8' block walls and the roof overhangs about 24". The overhang has allumnium soffit and facia with a metal roof. I want to insall under the overhang and because the unit is large I want to mount to the soffit like a ceiling mount. The area is not very large we are trying to cover, maybe a quarter acre. All the pictures, videos etc. show it mounted to the vertical wall or on a pole.