From way back in time when we used these type grader if the crown was there and if you stayed to the side of it , i.e., honored the crown, it would keep it's shape. If you went back and forth always being toward the middle (on top of the crown, you could wipe out a crown. If you have good draiage that takes water away from your road and if the road surface is higher than surrounding land you don't need a hugh amount of crown. Don't get me wrong ... you do need some crown to get the water off the travelway! It might be good if you notice that you are loosing the crown to have someone come in establish it again. And rock is good!
Leo
Ken,
I'm sorry I didn't notice that he had addressed the question to you until after I had given my 2 cents!
Leo