Thanks again Kirk. One more question. I notice the colour and numerical ratings now export nicely to Extensis Portfolio. When I remove these ratings in PM Extensis does not do the same. Is there a way I can adjust PM so it in essence "exports" a blank field? Thanks.
As far as I can see, PM writes "0" if you change the star or colour rating to none. So Extensis should in theory pick up the zero as zero, and remove the rating. If it does not, than it's likely a problem with Extensis.
However, did you reread the metadata from the files there? Extensis stores the imported photos metadata in it's catalogue, so if you change the metadata (incl. rating) outside Extensis Portfolio, after you have imported them into the catalogue, you will have to refresh the files from originals to reread the metadata. Not being acquainted with Extensis Portfolio, I don't know how it is done, but usually such option exists in cataloguing apps.