>I am attempting to use ipnat.. and nothing seems to happen.

Are you also running ipfilter?  

A simple /etc/ipf.conf as follows:

pass in proto tcp/udp all
pass out proto tcp/udp all

And don't forget to turn "ipfilter" in your rc.conf file.
That should make it work.

-- 
Phil Nelson                    NetBSD: http://www.netbsd.org
e-mail: phil@cs.wwu.edu        !gifs: http://www.gnu.org/philosophy/gif.html
http://www.cs.wwu.edu/~phil