It is true that the tests are limited to the vertical component of shock, but that is by design. The dominant axis of impact on the water is vertical, after all, and there are currently no standardized methods for assessing multi-directional impact mitigation. With only a small amount of lateral movement available, the laws of physics prevent a seat from achieving significant lateral mitigation. Even worse, as experience with testing of vertical impact mitigation has shown, there is a high likelihood that a seat capable of lateral mitigation in mild conditions might severely amplify impacts in moderate to harsh conditions. In any case the lateral performance will largely depend on occupant mass and impact magnitude, and carefully designed, systematic tests would be required.