For inconsequential reasons, I'm interested in Neo-Latin names for modern countries. It's usually not too hard to figure out the basic form (the difficulty mostly arises when you have to decide between an older form like Lusitania and a newer one like Portugallia), but what I find monumentally frustrating is the lack of information on vowel length. Very few Neo-Latin sources bother with macrons, and those that do tend to disagree with each other. You could say, "Who cares? just use your own approach," but I'm struggling to even find a consistent approach. Here are some of the cases that are bugging me – focusing, for now, on Europe:
I wouldn't have expected a long vowel here, but I saw one source that spelled it Bōsnia.
The analogy of Sarmatia and Dalmatia argues in favor of Croatia, but a lot of sources seem to prefer Croātia.
There seems to be no agreement on whether -aria or -āria should be used. I would imagine that both countries should take the same approach, right?
Jūgoslāvia? Jugoslāvia? Jugoslavia? I have no idea.
Classical analogies would seem to favor Lithuānia, but who knows?
I can't find any indication, but I think the analogy of Batāvia and Scandināvia would argue in favor of -āvia.
Polonia, Lettonia, Estonia
Classical precedent gives us examples like Macedonia and Calēdonia, but nonetheless several sources use Polōnia, so I'm uncertain about all three of these.
I saw one source that spelled it Rūssia.
I can't find any indication of whether it should be Slovacia or Slovācia.
I can't find any indication, but the analogy of Armenia argues in favor of Slovenia.
So… any advice?