I don't want to have 256 RTP ports when I will never use most of them. If you run the firewall tester, it takes too long and that time is downtime. I have a v15 site with 100 RTP ports: custom parameter FIRSTEXTPORT is 9000 and LASTEXTPORT is 9099. When I run the firewall checker, it checks ports 9000 to 9255. The firewall checker could be finished 60% quicker if it tested the correct port range.