Newbie having trouble with proxy setup

I'm trying to set up a proxy server using privoxy/ipfilter/ipnat. If I set up ipnat.conf with an rdr from the incoming interface to 127.0.0.1, I can get traffic flowing through privoxy.
What I want it to do (contrary to most setups) is to pass the clients' IP address to the webserver. At the moment, the web server is reporting the proxy's address.

I've set -hide-forwarded-for-headers and -hide-from-header in user.actions, but that doesn't make a difference.

Is my problem in privoxy, or something I need to set in ipnat? If anyone can point me in the right direction I'd appreciate it!