You should be able to see the back face also of a mesh by (in Poser) going to Render Settings >> Preview, unclick "Remove Backfacing Polys'. Alternatively you can change this setting per object in the Parameter window, Properties tab. If the issue is that the normals are reversed, those polygons should now be visible. That information should help you decide what to do next.

If you need to use a single mesh which will also show the reverse side (common with Dynamic clothing), a tip is to test your FireFly materials with 'Normals Forward' turned on (in the root shader). Many materials will look better with this enabled when the back side is visible.

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