If you're concerned about getting the fan on backward it can't happen. You can turn a radial style fan blade around and the blade pitch is still in the same direction. A lot of people don't believe that until they actually try it. I've not tried to mount one backward but there would likely be clearance & mounting issues if you tried it anyway.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.