I always get people who come in to my school from other systems and say,"I'm a third dan in whatever, what would I be in your school?"
My standard reply is, "You'd be a rank beginner. (like a white belt) Just because you're a pitcher, doesn't make you the quarterback."
I also tell them that their previous experience should enable them to move faster through the system, but that is also depending on whether or not they have developed bad habits, which may be so ingrained that it would be a hinderance.
He needs to empty his cup.
"My Gung-Fu may not be Your Gung-Fu.
Gwok-Si, Gwok-Faht"
"I will not be part of the generation
that killed Kung-Fu."
....step.