god, bringing back memories of the K2 forums. We actually had a good discussion about it, and this was prior to the rockered skis (hellbent and the like). A few people tried it with good results, including myself. I'll post up a tutorial when I finish rocker'ing a pair of old silencers..
But basically, you'll need to heat and bend in steps. Start out with your skis clamped together at the bindings. Then you'll want to slide some wood blocks between the tips and tails (start out with small pieces). Heat up the ski SLOWLY with a heatgun (aka Hairdryer), then let it cool and sit for a day or two. You can push the blocks in further or use bigger blocks and keep repeating until you get the rocker that you desire.
WARNING- The base, topsheet, core and edges are susceptible to warping. DO THIS AT YOUR OWN RISK. I AM NOT LIABLE FOR ANY DAMAGE DONE TO YOUR SKIS, BINDINGS, OR YOURSELF.
Enjoy.