I went through the Meopta site, and I know other people have said that they had manuals on there, but, as you say, it appears that is no longer the case. I guess I will try the Durst board and see what happens. If I can't get my good 50mm to focus I also have a 63mm El-Nikkor I could try, or I can just try the four-element Anaret that was in it and see if it is any good.
I measured the opening on the mixing chamber and it is approximately 54mm square, so it should be okay. I opened up the Meochrom head to clean it and it seems very tricky to get the mixing chamber out (they probably had a special wrench for assembly I guess), so they probably weren't expecting the user to be messing with it.
Speaking of messing with it, apparently the white specular material on the inside of the mixing chamber is water-soluble. I could see through the ground glass that there was crud on the inside, so I took the top half off the chamber and started cleaning the glass with a wet cotton swab. Unfortunately, wherever it touched along the edges the white material began to dissolve and smear across the glass, so I had to remove the glass altogether and clean it separately.
But now it is all clean and re-assembled, so I plan on trying it out in a few days.