Can you be the sole determinant about which pieces of information do and do not matter? Let me tell you: if I had to take that "40 days" literally, I would drop the whole claptrap and take up the atheist flag. That wouldn't be raining; that would be hydraulic mining. Nothing on earth would survive, not even an "ark made out of gopher wood".
You're not facing the problem. You can't write off any of the nodes and say "well, this one doesn't matter". You cannot know what other people know unless you ask them. This project of mapping the Bayesian networks of every belief system on the planet is difficult, insanely difficult, impossible. That doesn't mean you can skip over some parts and pretend they don't matter. Do you know what happens if you try to do that in quantum mechanics? You get the wrong answer. And considering what's at stake here, that would be devastating.
So, covering the entire surface of the Earth and putting two of every animal on one boat is feasible, but raining for 40 days without destroying the boat isn't?
The issues here are that if this happened, God would be violating the laws of physics and committing genocide.
In this comment thread, I gave the following idea, on the topic of a method by which one might judge the Book of Mormon from a rationalist perspective:
I would appreciate feedback on this idea, for an admittedly selfish reason: I am trying to instigate in myself a Crisis of Faith. So, here are the questions I pose to you: