X11 expertise on ancient HW sought... (4-plane visual (overlay) via X-server on MS-WIndows)

[Dimitris Theodoropoulos]

Sorry for undiggind this subject so many years later, but have you found a
solution to your problem? I am facing exactly the same issue, and i have
tried all possible windows X server options without success. The only
possibility I am working with is with a Mac OS X server, which reports a
5-bit visual.