Hi,
I'm not sure if it can be mounted upside down. I do see 3 screw holes on the bottom so maybe you can. Also, This is super bright in my apartment. That being said, if the distance between the wall to the projector in your church is bigger then an average apartment living room, then you will lose brightness and might be difficult to see.
Sorry for not being able to completely answer your projector.
I attached an image of the bottom of the projector for reference.