Internal OwnCloud with an external windows reverse proxy

Hello everyone. I'm new to OwnCloud, and I've gotten as far as setting it up and enabling ssl on my internal network. Now it's time to make it available outside. I already had a Windows 2012 reverse proxy set up for another application. Instead of taking up more resources in VMware, I want to reuse this RP for OwnCloud as well. The brick wall I ran into is a 403 forbidden error coming from the proxy. Google hasn't been much help. Has anyone had success using a Windows box as a RP for OwnCloud, or does anyone have ideas on how to get around this 403?