Oh man, if you like math, you should check out this paper by Gardner and Conlon: https://onlinelibrary.wiley.com/doi/10.1002/cplx.21446 where they did the math for CNS. I'll admit, it's beyond me.

There's also this research (cited by the author of Blowtorch Theory, if I'm not mistaken) supporting direct-collapse SMBH in the early cosmos here: https://arxiv.org/abs/1504.04042