Here's an Apache virtual host config that allows Apache to sit in front of an Arc web server via mod_proxy_balancer. I just took my typical Rails config and tweaked it slightly. You need to have the mod_proxy_balancer module loaded.
I've setup a pseudo IP of 10.0.0.71 and put www.lojic.com in my /etc/hosts file with that IP for testing. I'll try 2 Arc processes with sticky sessions later, but for one server the following works fine. If you don't have a bunch of other virtual hosts active, you could probably just use 127.0.0.1 w/o setting up the pseudo IP.
Having Apache sit in front of the Arc server allows using SSL easily, serving up static files directly for extra speed, etc.