This is usually very straight forward (or at least it was when I bought my Max some years ago
- Insert the USB drive you want as System Storage into the Max
- format the drive through the Max (Select the PopUp-Menu button - choose Settings and format the drive (ext))
- download the file Dune_service_init_system_storage.dsf and copy it to another drive.
-Run the dsf-file and it should be able to finde the empty drive and install the system files.
If this doesn't work, perhaps you could try with another USB-drive.