Xanadu class to me means what level a horse can successfully contest. A maiden winner can obviously handle the class (or pressure) of a maiden. Usually they can handle more, too. That is of course subjective. Makybe Diva can handle the pressure of any class race on this planet. To me, class is their level. You assess what that is (often it is better than where they are, especially when they are lightly raced) and if they are in their right "class" when they are entered, you then assess their chances against the opposition given the prevailing conditions. Class is not the "defining factor in the selection process", more it is a method of appraising a horse's top level, what it can handle and what it cannot. When a horse is outclassed, it doesn't run a close 2nd, it gets thrashed. Why? Because it could not absorb the pressure involved in racing in that field. If a horse runs 2nd, it handled the pressure, it just ran into another who also handled it but ran faster on the day. So, use "class" to define a horse's ability, to quantify it. If you like, you can quantify it in terms of saying "he's a class 1 horse" or "she's an open class mare" etc, and keep your own records of what you think their class is. Then, when a horse is out of it's class, don't back it, and if it's in it's class, assess it's chances.

Or, you can use other methods to define it's class. As people know, I use ratings to do that. That's my personal choice. However, the important thing to remember is to not go nuts obsessing about one aspect. Class defines what level they can race in, that's what it's for.

Cheers.