The Sorcery of Tuck Shrinking Sheet Metal

The simplest way to describe how metal moves or reacts when you shrink or stretch it is to imagine pizza dough. When you stretch the dough out to make a larger pie you'll see it gets larger AND thinner as you stretch it out. If you watch the process they start with a small, thick, round piece of dough that they kneed out until the dough is the desired thickness and put the excess material on the edges for the "crust" The same if they wanted to make the pie smaller, you'd need to gather the dough together creating bunches and smooth it all together until it was the desired shape. Metal reacts almost EXACTLY the same.