Okay thanks for tips. I assume that part of the reason for these scales warping is that "memory". The bonds and alignments within the material pulling and pushing to equalize pressures and voids. It seems likely that scales flattened upon creation are the ones that do this, but we see that some never do this, so perhaps some were not flattened but were simply cut from horn.. though maybe this is an over simplification.
Anyway I'll go ahead and jig it. Hot oil, that could be a better way, as it is possible hot water or steam dries out horn..