Like someone said earlier. If you are doing it just for looks, go ahead and crank them. But if you plan on doing any hardcore wheeling, then forget it. Being cranked makes for less suspension travel, so instead of flexing through holes and ruts, it will just bounce. You will find it especially difficult to climb steep hills if they are even the slightest bit rough because the front end will bounce and you will lose traction. I found this out the hard way.
For looks, go ahead and crank away.
For wheeling, don't even think about it!
Just my .02
-Dave