I do not think that opening up the passage on the valve body will help. JW designed that case to work with a full-tree or pro-tree brake, by adjusting the amount of fluid allowed to dump. This is their website with a phone number
http://www.racewithjw.com/about.php Why don't you give them a call?
If I were you, I would not let this guy touch my transmission any more. It has been 5 or 6 times and it is still not right and he says that he is going to charge you for this and that it might not still work, while he is experimenting on your valve body and case. He doesn't know what is going on.
Bill Mitchell