How many here have seen a broken axle because of over weight? I never have! I really do not think this coaches can be over loaded to the extent that you could break an axle. Most of the stuff you carry in the compartments are not heavy. Sure they take a lot of room, but most is simply not heavy equipment.
The manufacturers of these coaches know what kind of axles to put on them.
But there is something to think about on a Navigator. I test drove I believe it was a 2006 that they had for sale at Desert Hot springs. There was two things I did not like about it. It was forty foot with a tag, but the stiffness of the ride was not for me. I also did not like the Detroit diesel engine it had. I would rather have a Cat or Cummins. But I could be wrong about the engine, it is just that where I worked we had problems with the turbo's on the Detroits.
Beautiful coach though, inside and out.