my advice from before was a little off, as the masq file is simply a command list, not an iptables rules file like iptables-save creates.
to do this kind of thing i installed the portforwarding plugin.
It isn't a real simple solution, but if you can figure out what table you want it in, I'd suggest that you modify either the original template in
/etc/e-smith/templates/etc/rc.d/init.d/masq
with the exact command you want, or put it in a file like /etc/e-smith/templates-custom/etc/rc.d/init.d/masq/91adjustPortForwardLocal
making sure to choose a unique name for your file (and they are read in ASCIIbetical order to build the masq file) so that it doesn't accidentally replace something in /etc/e-smith/templates/etc/rc.d/init.d/masq
And I'd make sure to insert it before the default -j ACCEPT or whatever in the PREROUTING chain.
so my 91adjustPortForwardLocal file looks like (if you choose to do it without installing the plugin)
/sbin/iptables -t nat -I PREROUTING 1 -p tcp --dport 7080 -j REDIRECT --to-port 80