Thanks for the recent replies! Dann, I found a top in my parts box that looked a bit like the Speedster's top. After some pondering I am rather sure that it was a leftover from Heller's Mercedes 540K I built decades ago. Though it was too wide, too long and didn't follow either the curvature of the body nor the angle of my windscreen the necessary modifications were less effort than starting from scratch. Finally the right shade, however, is the most crucial factor for a convincing look of any convertible top IMO - I had to repaint this top twice.