I had mine done with the top rack about four inches from the rim and the lower rack about 9 inches below that. I use a heat deflector made from the lid, resting right on top of the charcoal basket, no holes in it.
Mine runs perfectly. I don't minion to start it, I have a door in the sidewall of my UDS and fire it off with a weed burner. The lower rack runs about 20-25 degrees hotter than the upper. She likes to cruise about 230 most of the time.
PNWBA - Hayden, Idaho http://www.facebook.com/BC2BBQ