Depends on the weight and the quality of the rack.
With just a sleeping bag, bivvy, and sleeping pad- no problem. I don't use a compression stuff sack, so the bungie cords I use have something to compress and hold in place.
I've had problems with denser loads shifting around while riding and loading up the rack with too much weight. (OK, next time just a regular sixer instead of a sixer of tall boys.
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