Generally you don;t have a foam luff in a gennaker. These sails are designed to be used reaching and downwind in light conditions.
 The foam luff is only required in a headsail that you intend to partially furl when sailing up wind in strong conditions. The foam insert helps to maintain sail shape when partially furled but it's still not the best, the sail is still far too full in the middle.
Cheers
Alan
Elyse SM437