I can't stress enough how important it is to keep your numbers small. To draw from recent history, witches.town was one of the more popular Mastodon servers in 2017 and 2018. In mid-2018 there were a series of disagreements between the primary administrator and the users. I can't speak to the nature of these disagreements as I wasn't there but there were multiple disagreements about moderation policy, and also the primary administrator (who I believe actually owned the server and its domain) said they were burned out on running the server. In the end, the site was shut down. According to archive.org it had about 2400 registered accounts in April 2018, shortly before the instance was deleted. 
I posit that 500 active, invested community members will not be able to achieve a values-based harmony or consensus. It's simply too big to be possible. My assertion is not backed up by any studies I have read but rather my personal experience in online and offline groups of all kinds. You cannot wrangle consensus from 500 people. With that many active, committed community members you will necessarily have at least a few dedicated members who feel investment and ownership in the community who are also extremely unhappy with the direction of the community.