Looks plenty good enough to me. Paint and sheet metal are cheap enough if one wishes to kitbash.

What is that thing that looks like a gong on the side of the barrel below the safety valves?

I found it in my first run QJ manual, but I can only make out a very few words in Chinese. It would appear to be an access port.

Greetings:
Sammy is correct: it is the cover for an access port, better known as a man hole. It is a much easier way to get into the boiler for inspections rather than taking off the dome cap, especially if the locomotive has a dome type throttle valve.
Russian decapods such as FRISCO 1630 at Illinois Railway Museum have them.
J.David

Great idea. Seems like we missed out on not standardizing it over here for our larger power.