This works with USBDLM as USBDLM.ini in the program install folder. You’ll need to set the VolumeSerial items to the serial numbers reported by the ‘DIR’ command in CMD, at the top of the directory listing, for each drive. The idea is that backups run directly to X drive, and then are mirrored (in StorageCraft, with ImageManager) to the Y drives, which are swapped.
[DriveLetters1] ; X drive, direct backup destination VolumeSerial=5011-1C44 Letter=X [DriveLetters2] ; Y drive, the first swap drive VolumeSerial=6430-826B Letter=Y [DriveLetters3] ; Y drive, the second swap drive VolumeSerial=6230-8823 Letter=Y