Only developed this for going to post office. do not think I have enough business for business postage yet (no link on your reply). To answer your question you will need to modify the class name in line 12
PHP Code:
class rm2ndsmlparcel { 
and this->code on line 22
PHP Code:
$this->code = 'rm2ndsmlparcel'; 
to what ever you called the module it should then work. Obviously you will need to set the rates correctly.
Good luck.