We know what you want, just why =\
Well anyway, same way you expanded to 120, just slap on 30 more levels. Quantum posted something of a guide around here for it.
u need a custom client with exp table move. Reference must be changed . the moved exp table must contain the additional level exp values.
Server must use the new exp table and checksum of max level 120 changed to 150 . IT is not hard, just time consuming