@evan I'm just about to announce my new account I am self hosting. I have a 4 letter '.me' domain because it's a personal instance, .social sounds good for an org.
I have a main website at x.me and soapbox installed at mastodon.x.me, but! I have setup webfinger redirects so that my account address will be @<name>@x.me, without the subdomain of mastodon!
Masto.host has a blog post on this and does it automatically on their hosting platform.