Nice job. Detail is good enough for a model that wouldn't be seen up close, and it surely looks intimidating. It doesn't have any armament (at least not yet), right?
As for balance, as I've once said on this thread, it shouldn't matter for that ship. It is supposed to be overpowered in universe, so I don't think that anything resembling balance is in order. One on one, it should be able to waste any other ship currently in FoTG. Missions can still be designed around such a powerful ship, though its utility would be limited. It was so in universe, as well. The idea of making ships that big was ridiculed by some Imperial officers (though out of Vader's earshot, obviously
), at least according to the "old" EU. It would be nice if it could enforce the "no way to approach it close up" with an appropriate amount of firepower, but it's probably a secondary concern now.