Actually I was thinking of the ring including its thorns only two centimetres high (1cm ring, 1cm thorn), with each thorn blends to a rod. The rod configuration stays the same.
Also take a look at Jan Brzosko’s presentation (pages 30 to 32), where he explains the concept of knife edge. This is a ring around the anode, actually with best results (for 45kJ) if that ring has negative height.
