With your second mask. Notice the top of the leg getting nyloned - because you drew gray above the stocking top. You grayed the whole skin, not just the parts with nylon. So - the shader dutifully draws nylon on the whole leg zone.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)