I'm 6', 170 lbs., so I'm not exactly Fat Albert. The problems with "modern" suits including most of BB's current offerings include:
1. The jacket is too short. It does not cover the posterior.
2. The buttoning point is too high. It should be near the natural waist. With a high buttoning point, the quarters flare out such that a triangle of shirt and the tip of the tie are visible above the trouser. This problem is exacerbated because....
3. ... The trouser rise is too low. Suit trousers are not jeans. They should sit near the natural waist as well, enabling a nice long and crisp crease from waist to cuff. There should also be enough room in the crotch to prevent whisker wrinkles and castration.
4. The combination of low rise and high buttoning point has led to modern ties being too long for practical use with a correctly cut suit.
5. The jacket lapel is too narrow. Flusser: “The lapel of a well-styled suit should extend to just a fraction less than the halfway mark between the collar and shoulder line.” This generally means 3.25 to 3.5 inches. The Fitzgerald is 3 inches; the Milano is even slimmer.
6. The trouser is too narrow at the hem. Again, suit trousers are not jeans. The hem should not get stuck under the tongue of the shoe. And the cuff should cover some of the shoe's lacing.
HERE is how to cut a suit, as modeled by a guy who was 5'8" with a 35" chest and 29" waist. This suit ain't no Milano: