Ian
If he is hitting it right then he probably doesn't have the correct shaft. In general, it's probably because the
shaft is too stiff which means with his swingspeed it is not giving the head enough time to square.
Tell him to speak to the Pro/retailer to try one with a softer shaft. Remember, the shaft and getting the right flex
is one of the most important things in club selection and its performance.
Let me know how it goes.