The easiest way to do this, if you're having trouble with transmapped hair, is to set the display for the hair to wireframe (Element Style - wireframe)

That way you can see the mesh even if it's facing the wrong way.

As far as I know (but I'd love to be proven wrong) there's no way you can see the backfacing polygons in preview otherwise.

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.