Again, this is also dependent upon the style of bass clarinet neck used. If you are so unfortunate as to be saddled with the flat angled, "tenor saxophone style" neck common in the past (and still prevalent on the less expensive "student" horns), then your head and neck is going to have a very "unclarinet" style tilt to it, this in order to bring the mouthpiece into your mouth at a useable angle.
Modern pro bass clarinets have returned to the premise that the player is playing a clarinet, not a slack jawed saxophone made of black wood, and allow the mouthpiece to enter the mouth at an angle more reminiscent of a regular clarinet. THis in turn allows the player to use the "simpering smile" style of embouchure that works the best at controlling the reed.
There has been a solution for the less expensive clarinets in the past, that being the line of adjusted angle necks offered by Charles Bay. I've used the bottom half of his first neck model for some thirty years now, and wouldn't be caught dead without it. He used to make both the two piece model (for Selmer horns) and a single piece neck (for student model Bundy horns; I don't recall if he offered them for Leblanc/Vito and Yamaha or not).