Simple question on fail over and config files

I have a primary and secondary running streaming replication with 9.2. Primary posgresql.conf file is slightly different than standby server conf file. If i create the trigger file to force the standby into primary mode, is there a way to make the new primary server  use a different config file configured for a primary after it becomes the primary besides shutting it down and loading the new primary config file? Or can we just leave it running as a primary using the config file it used as a standby?