The image below shows the sound board panel drying box before the last side was fixed. The air flow for this drying unit is from bottom to top, in a continuous loop. The total cross sectional area of the 14 air delivery ports from the fan to the panel drying bay has been set to be 12% less than that of the 150 mm X 150 mm lower delivery manifold cross sectional area. This minor flow restriction at the delivery ports forces the air flow volume per port to become very close to uniform. For same reason, the total return port area from the panel drying bay the return manifold has been similarly restricted. I suspect that panel drying equipment with non-uniform flow might well yield sound boards with uneven crown and longevity characteristics.