I found a thread about changing the .PZ2 extension into a .MZ5 extension to get the old P4 MAT pose files to show up in the material tab of P6.  Did that and it worked like a charm.  Kinda...

Unfortunately, now instead of affecting the entire character like the old MAT files, the new files only affect one part of the figure at a time.  It's a PITA to select every individual body part and click the MAT file.  I can't imaging that's what's supposed to happen.

Is there some extra command line or trick I need to do to make the old MAT files work the same in P6 as they did in P4?

If you don't have the files compressed, changing the extension to either .mt5 or .mc6 should work, I changed a V3 texture to the .mc6 and it applied properly in Poser 6.

Also, holding down the shift key and clicking on the material button will apply the material to all of the mat zones of the character.

I couldn't get the shift thing to work, but changing the file extensions to .MC6 seemed to work.

Thank you for the great advice.  Things are running much smoother now.

P.S. - Is the only difference between MT5 and MC6 the version of Poser?  Or is it something more?

.mt5 is a single material file, .mc6 is a material collection.