During the testing and development phase of the FREEK, we tested many 4 batten versions. They either had no ducking stability and acceptable lift or good ducking stability but no lift or explosive power (which is vital in all the new moves). The 5 batten version had both. Bucket loads of both.
One of the reasons to reduce the batten count is to reduce weight. Extensive use of eM3 keeps the sail weight low and allows us to benefit from a 5 batten layout – super smooth power delivery, exceptional wind range, more shaping options, un matched balance and stability when ducking and during maneuvers.