I'm not sure how tall he was, but if you look at the inner photos of the Derek & The Dominos Layla album, you'll see a photo of Duane standing next to Eric Clapton, who is about 5'10", and Duane appears 2-3 inches taller than Eric, so that would make him about 6' or 6'1", unless he was standing on a slightly elevated floor! Greg Allman is 6'1", so I'm guessing Duane was around that height as well.