Well here's the weird thing. I wrote that little script to manually build the maildirsize file on my system. I checked my maildirsize file before I made the above change and it was in the correct format (IE postfix or something else had modified it). Regardless I made the change to the config (box to dir) and restarted postfix. Sent myself an e-mail and nothing changed in the file. Deleted the file to let postfix re-create it (after sending myself a test). It did not.
So I ran my maildirfix script again and it created the maildirsize file. Sent myself an e-mail and Postfix updated the maildirsize file!?!
Something is weird here.....