Usually doesn't work too well. Shoot them like you would any other stage... as fast as you can without the disaster. You're national % will improve (as will your match points, crashing a classifier is bad for the match results).
Look at it this way... you can't shoot a match well by going "hero or zero" on every stage. Disaster is destined. So why would you want to move up in class based on, well, luck? You'll never be able to compete at the "hero" level.
Thanks for the insight. After my initial classification I have tried too hard to live up to my own expectations. Making B class in limited really put the pressure on me to perform. I've been trying to push the limit in practice then throttle back a little during a match to maintain some control.
Be careful about getting wrapped up in the "class warfare." Shoot your own match. There's no pressure other than what you invent and trying to "go for it" usually gets you the same result as when you "hero or zero" a classifier. Consistency is key.
Remember that the classifications are just arbitrary lines in the sand. If yesterday you were C class and today you became B class, then you can't expect to instantly be at the top of the B's. Keep practicing and you'll get there.
I love the classification system. It's provided me with continuous goals and a way to track progress. But once the buzzer sounds it don't mean nothin'.