vCloud Usage Meter 3.5 over the internet

Is anyone using VUM over the internet (with a firewall locking down 80/443 to only our IP range). For one customer we can't use 80/443 for vCenter as a webserver is using that port and the client has only one outside ip. I tried doing a port forward for 443 to 4431 but VUM can't pick it up even when I specify port 4431. I dont see a spot for specifying a different port for 80 though. Has anyone had success using port forwarding over the internet with VUM?

Thanks!