I agree. Is 50 ok. It might be important to write a special code that makes his first city the AV holy city is the AC somehow got that high without it being founded (Currently, if a religion is spread to a city before it is properly founded, then it can never be properly founded. Its holy city would never exist if Hyborem appeared too early.)
I would like a similar mechanism for CotD's holy city being wherever Abashi/Eurabates is built, but cause the cult to actually be founded in Acheron's city, and spread from there.