Keep in mind the following:

1. Harry must succeed via his own efforts. The cavalry is not coming. Everyone who might want to help Harry thinks he is at a Quidditch game.
2. Harry may only use capabilities the story has already mentioned; he cannot develop wordless wandless Legilimency in the next 60 seconds. Of course, Harry may find more clever ways to use abilities he has already been established to have.
3. Voldemort is evil and cannot be persuaded to be good; the Dark Lord’s utility function cannot be changed by talking to him.
4. If Harry raises his wand or speaks in anything except Parseltongue, the Death Eaters will fire on him immediately.
5. If the simples timeline is otherwise one where Harry dies – if Harry cannot reach his Time-Turner without Time-Turned help – then the Time-Turner will not come into play.
6. It is impossible to tell lies in Parseltongue.

Within these constraints, Harry is allowed to attain his fully potential as a rationalist, now in this moment or never, regardless of his previous flaws.

Of course, ‘the rational solution’, if you are using the word ‘rational’ correctly, is just a needlessly fancy way of ‘the best solution’ of ‘the solution I like’ or ‘the solution I think we should use’, and you usually say one of the latter instead. (We only need the word ‘rational’ to talk about ways of thinking, considered apart from any particular solutions.)

And by Vinge’s Principle, if you know exactly what a smart mind would do, you must be at least that smart yourself.

So what I mean in practice, when I say Harry is allowed to attain his fully potential as a rationalist, is that Harry is allowed to solve this problem any way YOU would solve it. If you can tell me exactly how to do something, Harry is allowed to think of it.

But it does not serve as a solution to say, for example, “Harry should persuade Voldemort to let him out of the box” if you can’t yourself figure out how.

…

I wish you all the best of luck, or rather the best of skill.