how critical is passive stability?

Then the obvious solution is to ensure that the
rotating body has length = to or < than the width. The
rotating cylinders can be stacked or strung along a
common non-rotational axis, but unconnected from each
other, allowing counter rotating cylinders of, say, 5
km diameter X 5 km length and strung along a 500 meter
diameter non-rotating tube. The structure can be made
quite long, perhaps as much as 100 km, though the
admission of light might become problematical, it
should be stable as no single rotating cylinder would
exceed the desired proportions.