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So again, which one had the good one and which one had the bad one?P-39 Expert, not according to the tests we saw ... I still wonder about those tests. One engine was sour or one was a "good" one, or they didn't use book power, or ... hey, we went over that more than 50 pages back. There's more to the tests we have seen than is recorded in them. Thet were NOT recorded in enough detail or perhaps even correctly. I doubt we'll ever know the exact nature of the test differences.
I can speculate, sure, but that's all it would be ... speculation. I'd rather not at this juncture. Suffice to say a stock P-39 is quite sprightly at lower altitudes.
Cheers.