You might reasonably question his conclusions but I don't think you can mount much of an attack on his scholarship. At least no one has to this point. Not Heise nor Robinson.
from Urban Underworlds, chap. 4, Thomas Heise, Rutgers University Press, 2011
I might also call your attention to page 315 of this thread, there is a bit of a discussion on this subject between E_R and RickM. Interesting stuff. By the way, my copy of Tarnished Angels which I found a couple of months ago weighed in at $75. ouch.