Never heard of Ubelmannia minninensis f. rubra
But I do know that we call that plant Ubelmannia buiningii
http://cactiguide.com/cactus/?genus=Ueb ... =buiningii" onclick="window.open(this.href);return false;
They are one of my all time favs, and all mine are flowering now too,
they flower several times a year
I have several on grafts and several on their own roots
They would be considered quite difficult, I use a mineral soil, keep them warm, and don't let them go completely dry in the winter for long periods of time. I think some people kill them by keeping them too dry in the fall and winter, when they do get rain in habitat.