Hard to tell from the photo you have posted, but it appears that perhaps you can only use one fan in this complicated space. If that platform extends out to the room, and you expect at least 7' for a standing person with a foot of clearance above their head, that really pushes the fan out into the room.

With these vaulted ceilings, the fans cannot be mounted to close to the ceiling or they don't more the air.

Additionally, it appears that all your walls and ceilings have been covered in drywall, so I'm not sure how you plan to get the electric to the ceiling to mount an electrical junction box.

Do you need a fan over the stairs? Unless someone is sitting on the stairs I don't understand why you would want one there?

ML

@maddielee - The fan will push the air down to the lower level. I have one in my cathedral ceiling, and it is wonderful in the summer! It makes the entire room and hallway cooler.

The electrical boxes are already in place, the place is more roomy that the photo appears, the fan is not for the stairs but for the rest of the room, dining room to the left and living room to the right of stair area .. I don't think I would have planned out things the way they were planned out but I am having to deal with it so .. do I go smaller fans, which means they can be a bit lower in the room or do I go larger fans but located closer to the ceiling. The fans are mounted on a flat section of the cathedral made especially for the fan, 16 foot mark and the actual point of the ceiling is about 1.5 feet above this.

You won't be able to tell the difference if you put up a 54" fan or a 60" fan when viewed from the floor. Your big dilemma, will be how long to make the fan down rods, and you just may have to experiment with that for this complicated room. If you view these rooms, you'll note that the fans are all mounted more than 9' above the floor, but not very close to the ceilings