Your cut-boxes idea is best. I would suggest removing the other two slideshows/presentations because I feel they weaken your overall pitch. Investors want to know you're focused, confident and dedicated to your idea. They wont necessarily get that impression if you're offering a download of your brain. But good luck!
The YC application does specifically have an entry for alternate ideas, so at least in this case it's probably a plus if anything. Plus, pg makes a big point of the way startup ideas change over time, so I doubt that being focused on one idea is too much of a point for him.
