Well, to offer a counter view, I've only ever used contact cement (UHU or Bostick) when I replaced my soft top. It's worked perfectly so far and my rag top has never blown away despite my short-burst attempts at the 230SL land speed record. I have no idea why you'd need a special glue, let a high temperature one or a special Mercedes glue (which won't be made by Mercedes in any case). The other good thing about contact cement is that you can clean it nicely away and, if you bugger the job up, you can pull it apart and start again.