If the diagram is a tree you may apply the Balloon Tree Layout (the algorithm is implemented by the NBalloonTreeLayout class) which provides better drawings of trees than the Radial Graph Layout. It defines the following properties which control the layout behavior: 

• ParentChildSpacing– determines the distance between parent and child nodes in the resulting drawing. 
  
• VertexSpacing– defines the minimal spacing between 2 nodes in the layout. If set to 0, the nodes will touch each other. 
  
• ChildWedge – the sector angle (measured in degrees) for the children of each vertex.
  
• RootWedge– the sector angle (measured in degrees) for the children of the root vertex.
  
• StartAngle– the start angle for the children of the root vertex, measured in degrees anticlockwise from the x-axis.