Update Might Fail if the dvd drive is disconnected and flag the xbox.The origional LiteOn Drive of my Phat xbox 360 now gives me open tray error.But I had managed to get the Dvd Keys off and saved the origional firmware. I use that Drive for purpose of performing updates.Once the update is successful I spoof the LTPLus1.9 Firmware on my BenQ Drive and I have been able to take it online as I wanted to get the Media Update only to play movies in different format.Risk of Ban was there but I am not too keen to get on live. I have not tried the following as I do not have a Slim but you may give this a shot :
If you have your DVD keys and origional Firmware backed up then get a BenQ or Sammy or any other DvD drive which is easy to spoof.Or You may get a spare Slim DVD Drive.Then spoof the stock firmware of 0272 on that drive. Connect it to xbox slim and update using USB.Once done take it out and spoof the LT Plus 1.9 Firmware on the Origional Slim Dvd Drive.