The diagonal cut is the Mitchell system chest cart to " house" the chest. To make a dart properly the cloth is not just cut. The pattern is opened up in a very specific way ( as seen on pg210 of the Mitchell system ) an sewn back up in the cloth.
The long cut across the front and the small cut across the chest is the remedy for an erect stance as opposed to just dropping the front from the shoulder. They also allow me to "sew tight" the bridal tape without shortening the front balance.
The Arrow at the waist line shows where I have given "sway" to the front for added front balance.
Below is where I have opened the back to give it "round length" over the blades. Just because a customer has a long front, as this customer does ,it does not necessarily mean the back will be short. Also I have closed the back at the waist to lift the coat seat so that it does not hit the customers seat.