Shirt fitting

[Gerry]

I agree with peterle. Although it would be a trivial matter to knock what you have into shape, you'll have a more accurate pattern (system permitting) if you learn to draft from scratch.

[Gerry]

I also have the Don McCunn book which didn't serve me well in making trousers, but maybe his shirt pattern is better.

That's not a bad method because it's very intuitive and uses one's own measurements. The caveat is that McCunn's system for a basic top/sloper is quite fitted, whereas a shirt is going to be a looser fit.

His method for determining the shoulder angle and drawing the neck is all good. Just take measurements for both sides to combat asymmetry. However, with the torso it's better to think of it as a cylinder with ease added in the case of a shirt; then literally draw it as a (rectangular) block. This assumes a 'regular' build - which you have (your photos show that you're not carrying extra pounds). Curvature of the side seams, and addition of darts etc, can all be done later to add shape.

In the case of someone who is slim(ish) then often there is little difference between the chest and seat measurement. The larger of the two can be used for the torso's circumference measurement to create our block. We just add the appropriate amount of ease to that measurement for the desired outcome and use it at all points (chest, waist and seat). This is how shift-dresses are typically designed. But the same principle applies to shirts: 'straight-up-straight-down' over the body, add shape in a fitting.

As a rule of thumb, if someone has a slight build, or if a fitted look is required for an average build, then 4 inches of ease is added to the torso circumference. 6 inches gives a more relaxed feel (though not baggy) for most. 8 inches for a loose fit, or if someone is on the heavier side. Go with 6 inches of ease would be my advice.

The hems of dress shirts are taken down to the crotch line. Casual shirts down to the seat/top of the pubic bone. Follow the above guidelines and McCunn's system is as good as any other. Edit: though the sleeve stuff didn't do it for me: a short cap is required rather than a more fitted draft. Plus the armscye shaping is questionable: the 'cross chest' measurement above the apex line, from the middle of the arm joint to the CF, needs some ease. Likewise the cross shoulder measurement on the back. IIR, it's all exactly fitted in McCunn's book.