The size? probably down to Sunspots and even Cometary nuclei.
Abell 520 Galaxy cluster collision, is a clear example of the clumping of dark matter (black holes) during galaxy passage through the center of the collision.
Galaxies lost their Galaxy Anchor Black Holes, ( GABHs)
In line with Quantum FFF model.
Most of the galaxies apparently have sailed far away from the collision.
This result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to the invisible substance, even during the shock of a collision “
see also: Bullet cluster with central DM core.
Black hole gravity and Fermion gravity is not equivalent in Q-FFF Theory.
Quantum Gravity on a black hole nucleus is adopted to be the result of only a single particle based axion/Higgs field (Casimir alike) pressure.
Quantum gravity on Fermionic matter is a the result of a combined pressure force between opposing Axion/Higgs vacuum pressure and (anti) Graviton pressure. see: http://vixra.org/abs/1103.0024