There are a lot of euphemisms or synonyms for stout such as plump, strong or portly. In modern slang terms, we can think they're mostly unkind like chunky or porker. When we pick Blue up all those come to mind. Though this post doesn't provide specific weight, our handling of Blue relative to his siblings leads us to believe he is the weight leader of the pack. Not only with weight, he feels solid!
As an aside, one of us believes that Blue is Ming's favorite. Now favorite may be a loose interpretation but Blue gets a lot of attention from our observations. Time will tell but we're certainly on the lookout.