Better create a new folder structure for all of those, which then gets granted full access for all (registered) users, or personal folders inside, for each one.
It's highly recommended, to set the recording path to be right outside of ProgDVB's folder structure. For this, you may create yet another place, this also should have sufficient disk quota available for users..
Best idea perhaps, to add a second physical HDD for things like this, as there will be a lot of quite big files to be stored, sooner or later...
ProgDVB would even record fine to a USB2 disk.
And, according to some test I did some time ago, it can run from (though not record to or have timeshift on) the USB1.1 connected XD card inside of my old digital camera, or a USB flash stick
You can set three recording folders at the same time, and if e.g. the first place is not available at the time, ProgDVB would automatically change to the second one, without any message.