Goodgulf:
The thing is - I'm pretty sure that the readers are going to think it's sci-fi, even if it isn't, and supporting equations just don't work in a spanking story.
"Even if it isn't"??
Well, I believe that such a story would have to take place in a future time in which humans have interstellar spacecraft capable of approaching the event horizon of a black hole, while at the moment NASA is working (slowly) on eventually landing human beings on Mars.
Set in the future, involving technology that currently hasn't been developed on Earth--AFAIC that's science-fiction.
Making the plotline conform to the known laws of physics, IMHO that arguably would mean that the story would be plausible science-fiction rather than partially fantasy... --C.K.