PerObjectCastDistanceRadiusScale The scale factor multiplied with the radius of the object to calculate the maximum distance a per-object directional shadow can reach. This will only take effect after a certain (large) radius. Default is 8 times the object radius.
Usage
r.Shadow.PerObjectCastDistanceRadiusScale [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.