Auto eject highspeed USB drive

I'm using a USB3 external drive with a BlacX box as external storage for making a copy of backup files that are also stored on a QNAP NAS.  The copy is being done from a virtual server using a robocopy script that runs as a scheduled task after the backup is completed.  After having gotten past the challenges with passthrough of the USB controller, everything is working fine generally with the copy process.

HOWEVER, I'm having problems with corruption of the file system on the external drives when they are removed from the BlacX. There is a large amount of data - over 2TB of backup files on a full backup - so I've configured the drive policy to optimize speed rather than quick removal, and I think this is the problem. Without that configuration it takes several days to copy all of the data, while with that configuration it finishes in about 16-20 hours, which allows us to complete the copy by the end of the weekend for a full backup that's scheduled to start on Friday at 6PM.  We've instructed the onsite employee (not a technical person) to turn off the BlacX box, then eject the drive, put the new drive in and then turn the BlacX box back on.  This doesn't seem to be doing the trick, as we're still having to reformat the drive when we reconnect it on many occasions.

I've thought of trying one of the freeware applications that are available from various sources to eject the USB drive programmatically.  Does anyone have any experience with these types of applications, or any other suggestions for handling this problem?