No, auto crossing isn't that hard on your K-member either. It's still on a smooth road. I agree, there are some K-members are stronger than others, and for different applications. You can ask D&D, QA1, or any of the other common drag race K-member manufacturers. They tell you up front that the stock K-member is way stronger.
If you want to see how week the suspension is on some of the drag cars out there, look at the tie rod ends on a top fuel car. They are like pencil diameter. That stuff is built to be super light.
Kurt