Lately I am getting more serious in snow skiing gates (SL, GS).
Snow slalom skis flex are measured in some different ways.
For example Atomic/ Salomon produce a large number of skis and then measure the flex figures per ski.
Based on the figures they pair them.
I used the 2007 Atomic SL skies with flex 38/27 and that is number of mm flex under certain specified load. (It is also refereed to when define the ski radius R=12,5m).
I would assume that this could be/is similar for competition slalom water skies?
After all they are hand made and must most likely have slightly different flex figures.