I used Clonezilla to clone the drive. Then Gparted to expand the last data partition to fill the rest of the drive. Gparted showed some kind of error, and had some trouble expanding the file system to fit the expanded partition, but I managed to force it.
It looked ok in the partition table, but I want to verify that the Disklavier is seeing the extra space - that's why I was asking if anyone knew how to see the total drive size using the PRC-100 or DKVBrowser.