Hi Rolf,
The spark, the starter, for the self tacking jib system on beach cats in Europe came from an ARC22 that was sold in France in the early 1990s "with a curved track". This boat owner was visited by several top sailors and boat builders in Europe after they had heard about the system. They made pictures and asked many questions of the owner.
The main purpose of the jib bottom batten is to keep the sail from getting too full while reaching. It does not compromise the jib sail shape. It makes it better. It acts something like a bendy boom on the foot of the jib. It is about a 3 pound compression batten.
With the straight jib track the jib sail is sheeted tighter in puffs. It is only sheeted tighter in direct proportion to the increase in sail pressure. This holds a more constant sail shape than doing nothing.
Bill