1/ Mine are plastic and fine, check for leaks when you have tightened up to ensure no gas leak. Put some soapy water around the connections and watch for any bubbling.
This is what I did with mine cost about £200 to do.
Took alot for fitting and lines. Line go about 25ft to my bar.
If you get stuck any more just give me a message.
How do i connect my gas line to my mixed gas regulator?
From the coupler I have a 1/2" to 3/8" connector which works fine. However, to connect to the regulator there is no threaded end it and is the same diameter as the pipe?