^Rademaker's design is the official design, so I would call it a little better than "supposition by a fan". But I see what you're really saying. The capabilities it has portrayed in the novels would carry more weight. The question is, are the authors following what Rademaker listed, making up their own stats, or some mix of the two?
If I remember correctly, Mark's own specs call for 26 or 26 decks. And in one of the novels, there already has been a mentioning of a deck 30-something. So yeah, the writers are doing their own thing.