Well, top hats have been known to fracture and break into two (know of a recent case with JRZ's!), but mine are ok so not due to this. The noise can be annoying in my car (at low speed) because I don't have any of the rear plastic trim, tray, trunk lining etc., so wide open.

 

I have actually had this problem as well. My noise, though, seems intermittent but very similar.

I actually attributed it to the gas door release cable being loose and tapping against the inside of the trunk. I taped that bugger down a bit better before I put all the junk back in my trunk after my last track day. I have not heard the noise since.

 

I think the clunking is from the spring moving around or something. I raised the car up a little bit and the sound that the spring and upper mount makes as it turns is similar sound I am hearing. After raising the car up a little bit, the sound seemed to have died down a little bit.