I have several different leather saddles and prefer the Brooks B17 Narrow. I bought a C15 about a year ago and the shape and fit was very similar to the Narrow and felt great in that regard but it was just too hard. I tend to ride back on a saddle and the Cambium just does not have the give back there that a leather saddle does. I sold the Cambium and bought a B17 Narrow Imperial model and it is heaven.
At least in my experience there is a definitive difference between the flex of the Brooks Cambium and their other leather saddles - even out of the box. For that reason I would not write off trying a leather B17. The OP's comments seemed to indicate that the design of the cutout portion of the Cambium may be the source of the discomfort. It is different than the cutout shape of the Brooks B17 models.
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Nothing compares to the simple pleasure of a bike ride - JFK