I've realized as I've been posting that I've been operating under certain assumptions that I never discussed with anyone and nobody else seems to have made a topic about it so that's what I'm doing.
Roughly, I've always assumed Hueco Mundo exists as a plane that has no real beginning or ending as if it were a sphere. 1/3 of it being occupied and under direct control of the Espada, 1/3 of it being Espada territory but not direct control while the final 1/3 being unknown territory.
I was wondering what others thought of this or if they had an idea of their own if they'd like to share