Separate thumbnail directory in Profile Gallery

I want to use a separate thumbnail sub-directory (.../thumbs/)for CB Profile Gallery thumbnail images.

I have studied the code in cb.profilegallery.php but just cannot see a way to do it. In the past I have successfully made some changes to directory and file naming and I am able to create a sub-directory (with an index.html), if needed, no problem. I just don't get what I need to alter to direct the thumbnail version of an uploaded image to a different location.

Could somebody point me in the right direction?

you would have to look in the function _pgProcessNewItem as it has most of the logic.

not sure if that is the only place.

Please note that each user has a separate folder already. I don't understand why you need to do this.

The reason is that I am using that structure for other functions in the site and it would be clearer for my users to have large and thumbnail versions of an image in separate directories.

I think I have narrowed down the place where the action happens to here:

* I can't get the post to submit with the code block in place *
It is lines 385-421 of cb.profilegalley.php v1.2 RC2... if anybody wants to look it up!

It looks like a $final_uploaded_tn_fullfilename string is prepared for the thumbnail but I cannot see how it is used. As a test I tried 'sabotaging' it with odd values but uploads work as normal. Is it all happening in another function somewhere else (imgToolBox)?