public bool UseRealWorldSymbolSizes {get; set;}

{
  // Note: call within QueuedTask.Run()
  {
    var def = pointCloudSceneLayer.GetDefinition() as CIMPointCloudLayer;

    //Set the point shape and sizing on the renderer
    def.Renderer.PointShape = PointCloudShapeType.DiskShaded;
    var pointSize = new CIMPointCloudFixedSizeAlgorithm()
    {
      UseRealWorldSymbolSizes = false,
      Size = 8
    };
    def.Renderer.PointSizeAlgorithm = pointSize;
    //Commit changes back to the CIM
    pointCloudSceneLayer.SetDefinition(def);
  }
}