I think Podlasie is decent as it is. Putting Jacwiec to it would make it pretty cramped for Volhynia (though it could be combined with Galicia
) and Yatvyagi is imo too east to be part of Prussia. Geographically Yatvyagi province would be around between Lomza and Suwalki, I'd say.
Of course it is open for discussion though.
Of course it is open for discussion though.