I just installed a LaCie DVD Lightscribe drive into my daughter's MDD G4.
The tray would not pass through the door. I had to grind away the bezel's plastic inside radius and then square up the corners with a flat file. Then I had to sand off about 1/32 from either side of the DVD tray so it would pass throught the outer part of the bezel.... a PITA, but it's nice to be able to retain the mirror doors. From the outside, it looks stock.
One other thing... I was replacing a dead Combo drive. I though it might magically come to life if I left it in the second bay along with the new drive. What it DID do was keep the new drive from coming to life. For a while I thought I had some serious bus problems. As soon as I removed the old drive, the new one came to life.
