Thank you! Finally completing my collection (serveral blue, black, white, and clear switches and, finally, browns!).
As far as the adapters go: I've tried several, but even those that work perfectly with my Model Ms don't fully work with my PS/2 Cherry boards. There is always at least one key that is giving false signals. On one board it was the print key. I only learned about that after looking through the log files. On another board it was the A key. And os on. But I will look into the wiki for alternatives and try some more. So far, I generally use PS/2 for my keyboards, except for my Das III.
As soon as I got my MX11800, I will report about it.