In 1977, astronomers R. Brent Tully and J. Richard Fisher established that the luminosity of galaxies is directly correlated with their speed of rotation. This fact supports the idea that the visible matter in the galaxy is specifically correlated with rotation. If the percentage of Dark Matter varied from galaxy to galaxy, then it should have a greater relationship to the galaxy's speed of rotation than the visible matter does, but the opposite is true.
In the Big Split model, the visible mass frame-drags (i.e. pulls) the local galactic spacetime into its same spin. That local galactic spacetime carries the mass within it, as it spins, making the matter within it appear to be moving faster than it actually is. Therefore, the Big Split model predicts that spin and visible matter(+black holes) are 100% correlated. The Tully-Fisher Relation supports the Big Split model.