With the help of Simon BUCH, I have recovered all the files. Mr Buch successfully converted the first of the files. With his sample, and the knowledge that it was possible, I converted the remaining files.
The core of the problem is to replace CR/LF (0D 0A) with LF (0A). That much I had already tried. But apparently it's crucial to reinstate the CR/LF after the <MakerFile 3.0F> line at the start of the line. That much I missed! Thanks to you all for your help, plus an extra doff of my cap to Simon Buch. Final score: all 5 files recovered, including diagrams Doug
