Good stuff from Regis, I am not a light wind rider (96kg) and am just joining the discussion to pass the time. My trying to push the limits on water starting stems from windsurf wave riding with undersized sails. The, perhaps comparable criteria, was the ability to ball up to lower the level of angular inertia to make the roll up easier and sinking the board to sort off pull it underneath you. The two factors did not go completely hand in hand and so you had to sort of pump your body up over the board.
Questions to Regis:
Do you have a similar feeling and, if so, are you aware of being able to time the body pump with the kite movement?
Do you feel that a low volume board is an advantage for the ultimate waterstart, even if it may have disadvantages elsewhere.
PS I think I see from the video that in addition you are pumping the foil whilst it is still on its side and you are just beginning to move and before you are up, does that over ride the above in your thinking regarding balling up etc.