I think it's time for him to change his mechanics and stance in increments . Practicing with the same technique is not going to help imo , it's a broken shot that needs an overhaul . I mentioned in another thread that his stance is offset with the left foot behind the right foot . He should start with that by squaring up and placing both feet more evenly on the line . See what that does and build from that , how can you hurt 33% anyway ? In fact I think he has to change it because there is no way you shoot that percentage unless your mechanics aren't working for you . A change is the only way he will see drastic improvement , got nothing to lose so make it happen .