Thanks for taking the time to read and reply.  Keep up the great work with Ubooquity!

I add another voice for a side file.  In addition to Clay's excellent reasons it's also practical from a data management perspective.  If you want to update the meta of your files, whether it's 1 or 10,000, the side file in each archive will have to be updated.  Which means reading the archive, potentially extracting it to a temporary location, updating the file, then re-archiving the file.  In addition to the time it takes, this will also cause the file to be "new."  So if you back up your files, you'll have to back the whole dang archive up again.  Or if you have the entire file on your device, you would have to redownload the entire file because a single 1K file inside the archive had a minor change.  Updating a smaller sidefile, for instance, will be quicker and won't require a full back-up.