didnt read all the posts, but I can add that a box that is really big will allow more possibility of the bike moving around in transit, greatly increasing chances of damage. You really dont want the bottom of the fork to be loosey goosey with lots of room, as it will get smashed back and forth into the box, putting a lot of unneeded forces into the fork and headset.

new bikes get sent packed solidly in the smallest box possible, partly for shipping costs, but also so that stuff is solid and not moving around and getting damaged.
Seriously, go to a bike store and ask to watch an unboxing, you'll get great ideas of how to properly box it and how to zip tie stuff in place safely, plus they'll be happy to give you the box and all the plastic protector things and foam. This is a win win for you to do.

other plus for the smallest box possible is that its just plain easier to get into a car, or taxi or even just moving around in the airport on a trolly and going through doors or passageways.
Been there, done that with all of the above. Would never want to use a "big" box just because. you think its easier to plop your bike into it.
Oh, also a big box probably has more chance of falling off the conveyor belts that take luggage here and there. I've sent my small box off on its own down a conveyor belt in at least one airport (Mexico City for sure) and a big box would imo be more at risk of falling off around corners and crap like that.