Hi Bob S,
Good plants and good names, except for the last one. Not flavicentra, which would have golden yellow
central spines and the flower would be a deeper pink, almost red in fact. As to it being m. dixanthocentron I have my doubts too, as I would expect the lower central spines to have some curvature. Your plant's centrals appear straight. It could be a more northerly form which tend to have shorter centrals and don't always develop a curved central. Also there appears to be only 10/12 radials on your plant, m. dixanthocentron usually has 19/20. Unless you have a collectors field number for it, which states your plants name or allows you to look it up to confirm it, it's probably a trade hybrid or at best m. supertexta form.