You thought wrongly.. Even fixed roof saloons have some chassis flex.
While the e89 is pretty stiff it still has flex. It's a cabriolet it's unavoidable.
The noise was simply from years of vibration. A quick tighten sorted it. No need for roof alignments etc..
Black Sapphire BMW Z4 sDrive35i
Mods: HiFi Tweeters Stubby LED Halos & Front Indicators DVDInMotion SmartTop 313 BMW Performance Alloys LCI Repeaters http://goo.gl/PF4nSz