And again if the sail develops lift instead of just being heavier, the vector of force for the lift is forward, in the direction you want to travel. Think about blown out, bagged out sails with or without battens, and why they cause heeling. While no extra weight is added throughout the life of the sails, (if anything the sails weigh less), the lack of airfoil shape after stretching causes heeling instead of lift. The question is: does the addition of the weight of the battens, offset the advantage of the ensured airfoil shape that the full length battens give you?
And by the way, I have gone full circle with additions to my rigging. I used to have an antenna and masthead light aloft, along with the necessary cable and wiring. No more, I don't want anymore weight aloft than necessary. I do have two full length battens on my new(ish) mainsail, and the draft stripe tells me that it is shaped nicely. If I were to purchase a new main, I'd get it cut to take advantage of the shaping that 4 full length battens allow, I'd even set it up to have a square head.