The biggest collection of known galactic black hole masses that I could find was at http://www.johnstonsarchive.net/rela.../bhctable.html
I have plotted them on a log scale of black hole mass, and labeled in red above some values of the equivalent radius in light minutes. You can see that the common cycles that I have mentioned of 3, 6, 80 and 160 minutes are also common black hole masses along with a few related values.



Note that the values are not accurate enough to use Kotov's method.