I've seen discussion on this, and observed it myself: there was some kind of change in the Hair Room that makes older dynamic hair look way too sparse in newer versions of Poser.

Tiny, for example, said he had to fix his furry animal products because the fur is way too thin in newer versions of Poser.  I think he said Poser 8 was when this started.

So, what is the fix?  Do you just increase the hair density, and if so, how much?