I don't know about the SLK, but the R129's automatic top can be raised or lowered manually fairly easily. In fact, it is not much more difficult or time consuming an operation than working the top of a W107 like the 560SL. But this is a moot point, because the R129's top is remarkably reliable. And if you are so very unlucky as to have something go wrong, the built-in diagnostics of the top's controller make troubleshooting easy.