Not sure what you guys are calling USB Mass Storage ?
I have a USB OTG Adapter that works fine with any recovery
I save all my nandroid backups to USB and install all my roms from the same device. I use a 32gig microSD and an micro adapter in the USB OTG it works fine... you can also just use flash drives in it the same way.
If you want links to the adapters let me know ..their really cheap