Greetings:

I have Poser 8 (presently), Vue 9.5, with some Cornucopia3d vehicles, and would like to add a figure or 2 to some of them.  They don't need to be hi res.  Perhaps they don't even need to be full figures, or if so, in a sitting position. 

Would pz3 or .obj be better for this?  Anyway, thanks in advance for any thoughts.

I think Vue support poser figures, even you can pose the poser figures inside vue.

U can use the Poser 1,2,3,4, figures for this. They are included in the Poser8 content files. Clothed and non-clothed figures from these older Poser versions still work in the newer versions.
With some texture work they can be quite good background figures.

Will do, thanks.

Quote - Perhaps they don't even need to be full figures, or if so, in a sitting position.

Would pz3 or .obj be better for this?  Anyway, thanks in advance for any thoughts.

With low res figures (eg P3 figures) you would save a bit by using obj files instead of cr2 files (with high res figures you would save a lot). If you edited the obj files to delete everything below the navel (which may or may not be sufficient for your purposes) you would save even more. There would be no advantage in using pz3 files, as these contain more data then a cr2.