This was accepted by the 2014 Plenary (editor to confirm exact wording)
Barney Townsend - GBR alternate delegate
S10. 4.19.1 The organisers shall allocate numbers or letters to each competing aircraft which shall normally be displayed on the underside of the right wingtip with the top of the numbers or letters towards the leading edge. The same numbers or letters should also be displayed on the pilot's helmet. On Paramotors the number shall be placed centrally on the underside of the canopy, top towards the leading edge.
In recent championships, numbers were placed on the cage netting instead of the pilot’s helmet. This amendment simply allows for this variation officially within the rules.