It's all becoming a matter of tip vs. tail rocker.
Salomon has it dialed with their rockers. You can ski a big line with tip rocker, and tons of it. But to stand up on your skis and keep them from super unstable, you need to have length, and even in pow, a ski with lots of tail rocker feels fidgity. K2 has some form of it on the new Seths, which have the Hellbent rocker in the tip, and the rocker from last years tail carried over. Granted, the new Seth isn't that great, and would benefit greatly from a stiffer overall flex. Otherwise the new rocker and shape is awesome. It's just too soft.
Think of a non or slightly rockered tail as a rudder. You want to have something behind you to keep things lined up when you are cruising.
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