From my experience - and I have no special knowledge, as I am not from IT - the PB Device Manager always works with USB sticks, and I have tried a few...
Firstly, PB have stopped the Autofs/automounting - and I find this a better option, than original OpenPLi or any other image, for various reasons.
I had many failures and/or complications with original OpenPLi and other images because of this!
However, if you install PB image and go to PB Centre and find Device Manager, in there you can do various things simply, elegantly, easily, efficiently (better than any other Device Manager I have tried!):
-initialise a USB device
-check a device
-mount it (wherever/however you choose it)
-format it (in a format of your choosing)
-create a Swap file and de-/activate it (choose size, device/partition, mode [ON or OFF])
-expand your limited flash!!!
I find it is best, as it gives you the most features, and more importantly, it gives YOU controls, so it is FLEXIBLE and you know what is where, in which format and mounted as which device etc.
Depending on what I use it for, I put my USB sticks into my PC first and I erase (all the) partition(s), then create 2 partitions, using EaseUS Partition Master Home Edition 9.1.1 (free!)!
The first partition (say, 500MB) I mount as media/usb - using PB Centre > Device Manager - and I use it to "Expand" the limited Flash memory of your F500HD, using the same PB Device Manager in PB Centre, easily and elegantly...
The second partition (the rest of the space on the device), I mount as media/cf (do not forget to edit the fstab file in /etc folder, to add the line as needed and save it, then reboot F500HD - sometimes it is necessary to do it twice or thrice, 'till it works!). To this media/cf partition/device I direct loads of picons (I make a picon folder on it), EPG, I make a subtitles folder for DDsubtitle player by DDamir.
That way my PBNIGMA flies and it is stable...
Depending on how big and fast your USB memory stick is, you can even use /cf for Timeshift or recording stuff to it...
Anyway, I have described the whole affair in some detail in my "guide" on some 80 pages, with plenty of images, so anyone can do it. And I mean ANYONE, no matter how uninformed!
It's here:
http://www.sat-universe.com/showthread.php?t=218066
Use the latest PBNIGMA, if you choose to do so. It's here, in this forum's sections...