Jon, stone fabricators are the bane of my remodeling existence.
My favorite story is from the jobsite of a contractor friend of mine....he called to say that the stone guys were there, installing the slabs, and there was a small problem.
I knew something was coming by the tone of his voice.
One run of cabinets was a bit out of level. The GC said to the stone guys "Don't worry about this, they're a bit out of level, but they are flat....just lay the tops right down on the cabinets as-is, and don't worry about shimming anything." Later---he hears a "crack!". The stone installers started levelling up the slab by running drywall screws in from below the slab and tried to lift it into place.