this can be done by using the File Read/Write Test Chain and selecting the source path as /dev_flash2/etc/xRegistry.sys or /dev_flash2/etc/backup/xRegistry.sys and destination as /dev_usb000/xRegistry.sys or something. these can be typed manually, or they may be in the dropdown...i forget. You could also add that path to a dropdown option.
for PETT, since it IS a tutorial based setup, will need to first run the Get Filesize chain using same source path and enter that value into File Size box in hex format when using Read/Write chain.
both these chains are located in the 2nd row from top labeled "File System" in dropdown box
it probably seems more difficult than necessary, and you would be right. we have internal tools that already dump/inject the xregistry and automatically get filesize, but it will probably be rolled into the v4 Modder Tools in the future