I'm doing the same for vsftpd (for portscan reasons) and was wondering: why do you need to change the /etc/services file?
I can't explain exactly why... but, if I had changed default port of echo service to 80 in /etc/services it started to work. Maybe echo in xinetd is taking port assignment from this file.
...and how do you change it (i.e. what do you have to change)