I'm very slightly built as I cycle about 250-300km a week. Now I love Italian soft tailoring but one lesson that should be learnt very quickly on this forum by all is that you cannot always wear what you love, you have to wear what suits you and enhances your body shape. If I was wearing a very soft Italian style garment you would see my torso for what it is, i.e. hardly any shoulder mass and not much of a drop between chest and waist. What the British style does for me, however, by extending the shoulders slightly then building up the chest is mask that very well indeed.
I don't personally determine the correct amount of extension, a job best left to others...
A few examples of my own -
New & Lingwood MTM: