It depends on the length and position of the battens relative to the luff leach length at the point where they are positioned. That is at the bottom a short batten is essentially on the leech where it needs no shaping. At the top it needs shaping to match the shape of the sail. Probably you can get the end pieces and a length of batten and then trim the end down so that when it curves it takes a sail foil shape. You can test this just by bending it. I imagine that you would have to do this anyway rather than have a standard unit. It is easy to do and yes it makes a difference to sail shape and so speed even for a cruiser.