I had the opportunity to talk to some folks recently who dried southern yellow pine. The subject of venting came up. They use only a few large vents on each side of a double track kiln. All the double tracks I've seen in the northwest, have several per side. It raises the question of what is better, a few large vents or several smaller ones. For example, would four 24"x60" vents be any more or less effective than ten 24"x24" or twenty 16"x18" ? We dry both DF and HF with conventional schedules, no high temp ones.