Thanks All, I wanted to think that it was a function of the soundboard crown increasing more on one side of the unison than the other. If it did then the pattern would reverse on the more trebble (Down hill) side. It didn't seem to do so to as large a degree, though it may play a small part. I really like the explanation of the plate moving. It seems more plausible to me, especially after reflecting on how the strings are connected to the plate. I find it hard to believe that the cast iron is affected by humidity, but it is in direct, clamped contact with the rim and the beams, and the belly rail. It seems likely that these put strain, torque, or tension or a combination, on the plate. Thanks for the mental workout. Larry Messerly, RPT
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