While I cannot be sure, I believe it should be about 3 1/2". This is what my Alpha Gen 2 came out to be. An easy way would be to take 2 paint stir sticks and put them on either side of the drive, under the flange that would sit on the stand, and then measure the width. I would make it a bit wider to give you plenty of room. I wish I could be more help to you.
