I'm pretty sure my plinth is kicking about. I won't be able to check for 2 weeks though. I take it the 4x mount bolts are still intact? I only have 3 of mine as one had been cross threaded at the factory and took some persuading to come out.
Since you guys have to display a front plate, how about mounting it on a thick piece of dense, closed-cell foam that would help absorb some of the impact force in case of a slow speed collision rather than directly on the bumper as some of you have done?