How fast transmapped hair will render, at least for me, varies immensely depending on the geometry of the hair.  Stuff with lots of layers of geometry takes huge time, but simple stuff like Kozaburo's models tends to render a lot faster.  Part of the problem has been that some hairs have their specific min shading rate set to zero, which I turn up to 0.5 or 1.0; I think I've gotten some speed improvements from disabling texture filtering for all maps on the hair materials also.

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