According to Kain's little write up from a while back, the Cobb and Hotchkis rear bars have slippy bushings (they're not bonded to the bar and instead use collars to hold them in place). This means that the bar would move on the ID of the bushing instead of forcing the OD of the bushing to move against the bracket.
Whether or not that would make noise too I can't say...
Whether or not that would make noise too I can't say...