With b4, the install correctly detected my Matrox G550 and configured it for single-head without a problem.
I still did not get a test prompt, which Pixel explained previously happens for cards marked as having a problem resetting their buffers. He said that the G450 was flagged that way and that the G550 has being handled as a G450. I'm not sure whether the G550 is now flagged that way because it actually HAS the problem, or because it inherited the flag from the G450 definition.
