The Great Kingdom of Finland
My new king's stats aren't that good thou, but he got the crown just couple years ago so he better improve.
Yes, I own province middle of Sweden. I actually had couple more there, but lost them to Swedes some decades ago. Ruthenia is also getting scary big, and can field much bigger armies than me. And they don't like me. Well, Swedes are neither very fond of me, so I better hope they won't work together
But I have survived quite well, with homeland defense bonus, attrition and use of terrain, even superior forces can be beaten. Swedes actually tried to assault me several times over the sea with their 15k troops. I had ~6-7k troops sitting on shore pushing them back to sea time after time. Also, I have very good relations with Perm, the only other Suomenusko kingdom, who have even volunteered to join my wars. I try also help them when they need it.
Here is the map screenshot:
http://i.imgur.com/rXmoLXm.png
Massadid are the big blob in Middle East.
Also Great Moravia is actually Dutch kingdom, ruled by van Vlaanderen dynasty
Some provinces have even assimilated by now.