Three hundred capacity is the whole argument
Three hundred is not a round number somebody picked. It is where a guarantee starts covering the van, and it is also where the promoter stops carrying the risk personally.
Every band in this magazine has crossed it, or is waiting to. The crossing takes about two years, unless it never happens at all.
The rungs are real and they are specific, and anyone who has been in a band can tell you where they are without being asked.
At a hundred and twenty, everyone in the room chose to be there. You can hear individual voices between songs. Nothing is amplified except the vocal and possibly not that. A band at a hundred and twenty is learning whether its songs work, which is a different question from whether its performance works, and it is the only room where the two can be separated.