Friend is swinging too far inside out

[vjcapron]

I'm meeting a good player at the range this evening to help him with his swing. This guy is swinging too far inside out accross the target line (he's under the plane line coming down). He can shoot 69 one day and 80 the next. He can block it, block fade it, or flip hook it. Starting the ball left of target and gently fading a shot back towards the target is definitely not an option for this player at this time.

I don't have the energy to drag my plane board out of the basement tonight, but I may have to do so.

Does anyone have any other drills, thoughts, or concepts that will help inside-out swingers get more on plane?