I'm following the directions in your but running into a problem each time I try.
When I get to step 5, Adjust Dropbox’s Preferences, after I change the Dropbox folder location to the Vault folder which I've set up inside my Home directory, I get an error from Dropbox: "Error with selected folder: Target folder is on a device that does not have enough free space" ()
The thing is, disk space should not be an issue. My Dropbox folder is 29.32 GB and hard drive has 122.38 GB free space.