I think there was only one holy site for romuva. From what I readed the holy site was in Nadruvia (Instelburg) the wikipedia tells it is in western sambia.

Well, I based it on the CK2 Wiki info[ck2.paradoxwikis.com].

If you're still maintaining this at all: maybe hide the "convert to" decisions behind a single decision, something along the lines of "Open religious debate" or something? Once your empire is sizeable the decisions all kinda clutter the decisions menu, so that plus a decision to hide them again ("End religious debate") would be nice.

Thanks for the suggestion, I can definitely see the clutter when you own most of the world, so will implement this in the next update, which I am working on for release with Emperor 1.30 expansion.
I have been working on making an event based Holy Site bonus system, so you can choose up to 5 bonusses like the Coptic holy site system.

Glad to hear, looking forward to it!