[Zubersoft]

You are correct - if you have an Android 4.4 device, then the only location you can back up to on removable storage is /<path to removable storage>/Android/data/com.zubersoft.mobilesheetspro/files. You could try creating that folder path to see if it works, but I can only say with confidence that this works on an SD card. I don't know if it works on a USB stick. 

Mike