If your bars are moving after hitting a bump, you have mismatched parts somewhere. Either size or application.
I've never had a set of bars slip (that wasn't crashed), not even on dirt bikes where I'm jumping 5-10 feet in the air. That's old dirt bikes, not the ones with 2" of travel and seem to spend more time in the air than on the ground. So if a bar is going to slip, it's going to be on those old klackers slamming into the earth after a jump. There's a reason we pretty much all used to wear "kidney belts" when we went for an afternoon of dirt biking.
Most through bars will have a knurled section on the bar where they engage the bar clamps. This gives them plenty of "bite" when the clamps are tightened. If your clamps are smooth and the bar is smooth chrome, you're already starting out behind the 8 ball...