I recently had a lesson with a local PGA Pro. He noticed something which I have in the past - I tend to drag my short irons left. He suggested it may be an idea to have my short irons slightly flatter than the rest of my set.
This seems like a good idea, I just wasn't sure where I should stop or should they be graduated. For example 6 - 8 iron 1 degree flat and 9 - PW 2 degree flat. For the avoidance of doubt I currently play AP2's which were custom fitted but came back as being standard lie.