I get that you want him to find something that works and stick with it... but you told him to dump what he has, with no idea whether the mouthpiece or horn is in any way wrong for him... and I do find that irresponsible. If you are, as you say, not an advocate of the mouthpiece safari or jacking your gear around, then at least determine whether what he has is suitable first.
I did apologize for picking on your posting, and perhaps it would have been better had I not quoted it, but you are not the only one two suggest a change to something "middle of the road" sight unseen. It's a limitation of forums. You only know what the person tells you... and if you would have met him in person and heard him play, you might have said something completely different.
The advice is not necessarily wrong but it's not necessarily right, either.