Somebody call
Few things about tyres, they actually act as a form of suspension, so you don't want them to hard, you need to keep contact with the floor over small undulations. Secondly you need enough give in the tyre to get them warm enough so they work for you. I actually run my ninja tyres in the summer softer than the recommended because when i'm on it, they have enough heat in them to come up to the correct operating temperatures, otherwise if I ran them harder they would get too hot, then become less effective.
Some of the tyre pressure issue is keeping a decent sized contact patch, but alot of that comes from the profile of the tyre and the width of the rim it's fitted too.