There is much more than meets the eye to the concept of "the slow line fast."
It is not about a line, a turn shape, or a speed! It is a mindset, an attitude, an all-encompassing paradigm that cannot be understood by cursory examination of the surface meaning of the words. And like any true paradigm shift, it doesn't arise from mere rational discussion or understanding. It must take place deep down in your core! I'll throw a few more teasers at you.
I should remind everyone that no one has yet quoted my actual full statement that is often shortened to simply "ski the slow line fast."
"Good skiing means skiing a slow enough line as fast as you can, when you can."
THIS is the full statement, and the word "enough," the qualifier "as you can," and the final clause "when you can" are ESSENTIAL to its meaning!
There are times when a straight run is "slow enough"--it depends on the slope, the conditions, and the personal definition of "slow enough" of each individual skier at the moment. Remember that "slow enough" is a state of mind--it does not in any way imply "slow." Nor does "as fast as you can" imply "fast"! For some skiers, a "slow enough line" is a very fast line indeed! And for others, even a very slow line is not slow enough.
Nor does "a slow enough line" imply any partcular line. It can involve large turns, short turns, a variety of lines through moguls, and even applies to the tactics of half pipes. And, while these "good turns" are definitely not INTENTIONALLY skidded, they are not necessarily carved either. They are as carved as possible, given the equipment, conditions, and skill of the skier (hence "as fast as you can"). But Hermann Maier skids many feet sometimes as he flies through a downhill course, and beginners in their gently brushed wedge turns are certainly capable of skiing "a slow enough line as fast as they can."
The alternative to skiing "the slow line fast" is skiing "the fast line slow"--i.e. with the brakes on. Skiing "too fast a line" implies one of two things: 1) you are going too fast, or (more likely) 2) you are skiing defensively. Defensiveness, as a habit, is is hardly characteristic of good, or expert, skiing! (Although certainly, defensive, braking skills must be in the repertoire of the expert too, for use "when you can't"!)
Who would argue against the notion that great skiers habitually ski OFFENSIVELY, as opposed to DEFENSIVELY? But "offensive" does not necessarily imply "aggressive," and "defensive" does not imply "timid." Many very capable and very fast skiers are merely "aggressively defensive." They brake HARD! They fight the mountain aggressively.
The very moment you start to ski "too fast a line," you will become defensive. There are no two ways about it--it is not a value judgement--it is true by definition. "Too fast" is your own personal threshhold, in any given situation, at which you become defensive. It is true of beginners, intermediates, and World Cup Downhillers, in wedge turns or parallel, on green runs, blue runs, black runs, mogul runs, trees, steeps, chutes, powder bowls, and cat tracks.