I noticed a thump noise coming from the left side of the soft top on my Roadster Sport. It happens during acceleration, slowing down, and suddenly stopping. After several visits to the shop (and they are extremely nice at Menlo Park, CA), I figured it out. One of the black pins that sits in a groove at the edge of the soft top rattles causing the rump noise. I added some masking tape around the pin, to make it fit snugg, and the noise disappeared. Menlo Park is working on a more elegant solution.