Man-portable heavy bolters are canon.
Okay, after checking out the Necromunda rulebook (which is free, sweet!), I found this under Heavy Bolters:
...most gangs have one or two fighters who carry heavy weapons. These individuals are known as 'heavies' on account of the weapons they carry and also because they tend to be big, muscular fighters able to bear the weight of their weapon, ammunition and spares.
All heavy weapons described below are weighty, cumbersome affairs which take quite a bit of physical strength and energy to carry and use... etc, etc
Heavy Bolters:
...They are extremely bulky and are often known as the 'back breaker' by those who carry them...
So... basically, it does sound like they can be wielded by humans, but only exceptionally strong humans. In IG terms, I guess what this would mean is that I could make them usable by IG, but they would of course require two hands, and their weight would be some ridiculous number like 40,000, so any IG wielding a bolter would basically be stationary during combat.
Also, don't think I'm trying to argue for the sake of arguing. I appreciate your input on the mod, I am trying to make it as canon as possible. It's difficult to piece together stuff like this from all the disparate rulebooks, so it helps when someone who knows more about a certain area steps in.
Also, speaking of feedback, it would be really helpful if anyone playing this could give me info on Chaos sieges. What types of troops did they send, how early, were they too hard, too easy, etc.
ferrocrete? Wasn't it rockcrete?
Ferrocrete is a reinforced version of rockcrete... they're actually both in the mod :p