I am able to do the port forwarding rule I need with the GUI but for the other bit, this is what I was trying to achieve with the GUI
iptables -t nat -I POSTROUTING -s 10.0.0.2 -p udp -m udp --sport 3074 -j MASQUERADE --to-ports 40000
I’ve resorted to using a custom rule in /etc/sysconfig/firewall.local
All is working well 