A negative Z value would seem to be the obvious culprit, but I'd already checked that. However, it's always worth double checking, so I tried simply changing the sign of the Z Component output before plugging it into the Z Value input.

Network snippet and render attached.

Judging from that I don't think it's just a wrong sign.

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).