I'm having a similar issue. I've tried just about everything I can find on the internet. I can't seem to find a reliable way to direct a user to the folder I want them to use for uploading files. And when I do get things to run, they're plopped into the root directory, with no access to anything. Nothing shows, they can't create files/folders, etc. Once or twice I got a different folder to mount, but then they had access to everything, and that's not going to work.
A good explanation on how to set up users and either a shared folder, or individual folders for them, with appropriate permissions etc, is much needed.