Personally, I'd transfer the database files (or everything except the COH files, really) to a thumbdrive and move it from the most recently updated version to the older version. You can get fancy and make a 'sync' with a backup program or something, but I don't think this'll take more than a minute or two each time you sync them.
I don't think PChat can run from a cloud folder. (Certainly wouldn't hurt anything to try, but . .I still doubt it)