Spot on. This is fun to watch though. I've actually had to reach over and straiten somebodies head once, they wouldn't believe me they were tilting their noggins.
:rotfl: I definitely had a some headset tugger students. Instructors here have criticized me for it, but I find it necessary if they don't listen to repeated verbal instruction. I don't mean a slap in the head, just a gentle pull/push on the side of their headset.
To OP:
Since you haven't replied to the questions I don't know how useful we can be to helping you with this. However, here is a list of ideas:
1) Teach him to relax and look at the horizon like he is watching TV at home. Even bring in a sweatshirt to stuff between the door and give him an arm rest.
2) Cover the instruments. Tell him the horizon is eye level, like it would be at the beach, driving down the road, or any other time he has seen it on the ground. (It changes by 1 degree between ground level and 4,000 feet (Source: Stick and Rudder))
3) Once he is relaxed and focused on flying by the horizon get him to start doing some turns. Make sure he stays relaxed and build up from there to steeper and steeper turns.
I have found most new guys will go well beyond 30 degrees because they are so focused on that horizon. Often they will descend because they keep themselves feeling 1G, which we know is a descent when you are banked. That is simple enough to correct by later adding in kinesthetic or flying by the seat of your pants.
Keep repeating and overemphasizing the first step, RELAX. Good luck.