You'd better be one, if you write it. First, you'll then have to specify which sect you belong to - I'd rather not wager on the "incorrect" one. Second, one must sign a paper as part of the visa application that you understand that lying about your religion (among other things) can lead to very inconvenient circumstances.

Whereas I don't see the Saudis examing the depth of your Christian belief, I'm quite sure they have a few specialist when it comes to the followers of Mohammed...

Of course I always wonder if "pedestrian" would be an acceptable option