We have had better success with full tension. Shipping without any tension in various temperatures and humidity levels allow the neck to move in any direction, not only back bow, up bow, but side to side, which is difficult to correct. Above all, the neck must be supported to maintain alignment. We would prefer to ship in a hard case, with humidipaks so that the humidity fluctuation can be minimized. We have also received new guitars from various regions without any tension, some were unplayable. If we compared the under tension, versus no tension, the under tension tends to survive. If you feel that you are shipping to a high temperature/high humidity region, you could back the tension down by 1/2 step.