I would say 6" or so from the bottom would be fine. Mine is about that and it works fine. I checked it against a dairy floatey there and it was within a degree...
On Tap (Nitro): Chocolate Palomino
On Tap 1: Blueberry Blonde.On Tap 2: Imperial Red.On Tap 3: Moonless Midnight Hillbilly RIS
In Secondary: empty for now
In Primary: empty for now
Next up: Gold Dust Pale, Boxer Strings Nut Brown