While the low rez geometry is almost exactly the same as whatever was subdivided to get the final V4 mesh, and to the eye it's impossible to tell these apart - the vertex count is not what it should be if that were the only difference.  If I remember correctly, the low rez mesh has a couple hundred more vertices than it should, implying that some extra geometry is present and this will screw up your vertex order, I don't think your plan will be practical.

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