I've got Kindle 4.1.0 Firware (on Kindle 4 non touch) and I'm trying to use newest Doukan 4.7. I've copied DK_System, data.tar.gz, ENABLE_DIAGS and diagnostic_logs to kindle, ejected device, unpluged usb, restart kindle. I goes to "D) Exit, Reboot or Disable Diags"> “R) Reboot System” > “Q) To continue" and then during installation appears "Device is Kindle 4 WiFi (K4) (OK, DuoKan is ready for the device) ... NEED 48MB, AVAILABLE 0MB, NOT ENOUGH SPACE, SHORTAGE 48 MB, REBOOT in ... seconds...".
I've got stock firware with none modifications, and on the device is over 1gb free space.