My brother has a set of K2 Hellbents. His comment is just to get them longer, so you have a longer section of edge in the hard pack and because of the rocker, they are a dream in the good stuff. The rocker also negates some of the difficulty of turning a bigger ski because so much of it is off the ground. This would lead to a heavier ski.
Another option is to surrender to the fact that if you want one ski to one thing very well, you will be sacrificing something else. So if it is a powder day bring out the rocker, if it is not, bring out the cambered ski.