Custom ports HTTP, HTTPS on back-end servers

Hello, i am new in Forti I'm tryed to find way publish the Lync service via FortiWeb. The back-end Lync web server use 8080 for HTTP and 4443 for HTTPS. But i can't find how to create a Server Pool with two custom ports http/8080 https/4443.

On the MS IIS ARR proxy it's simple, create a Web Farm with the needed custom ports.

Any ideas? It's no not supported? 

p.s. sorry for my english)