Prominent chest - pattern changes

While browsing through a sewing forum, I noticed over and over the plight of adjusting a pattern for a full bust. There are many solutions offered both online and in many of the sewing books, yet many people still struggle with making sense of it all.
Here's a little sample of what I did to deal with a garment that needed more room in the chest, but fit well in the front length, armhole, neck and waist.
Whereas in women's wear, darts are an accepted way of dealing with shape, the challenge with men's costuming is often how to hide the shaping in a garment, in order to keep the traditional construction format.

I recently fit a doublet and while pinning it up the centre front, I found that it closed on the line at the neck and at the waist, but at mid chest, it would not.
It went off the line there by 1.8 cm.
The person I was fitting had a prominent pec area, and that was the cause of the gap. What often happens with a full chest is that there is a lack of length and width.

I had enough length in my pattern for the full chest so I am only correcting for width.

You can see that the pattern CF line is not straight, but it is curved already from the mid chest to the neck. This is basically a dart, which is masquerading as the CF seam. I did not wish to increase this CF "dart" by just adding the extra at the CF line and tapering it off to the waist and neck. 

Now, I split the pattern vertically through the mid chest, and separate the pieces half the amount of the gap. I need this much more at the mid chest level but in splitting the pattern I have made the neckline  larger and have increased the length of the side front seam. I don't want that, and so I need to modify the pattern further. I need to close the gap!

So, here you can see that I have made two cuts in order to further modify the pattern. One is at the chest level, and the other one is cut diagonally from the side front seam to the mid chest. 

I can now bring the neck back to the way it was and also close the gap in the seam. What happens though is the CF opens up and gains some length, and the side front seam also had a small increase.

Depending on your fabric and method of construction, you may be able to ease in those small increases. 

Here is another option. This time only the horizontal cut at the chest level is allowed to open up as the neckline and seam line openings are closed. The increase in width at the chest is maintained, the neck and waist are kept as they were. 

I am making doublets backed on cotton duck so easing is not easily accomplished, so I opted for this method in the under structure of duck, and used the previous method for the fashion fabric layer. 

The horizontal dart is cut out completely and the raw edges are butted edge to edge and zigged closed with a strip of fusible tape to reinforce the join. The outer fashion fabric is applied over the shaped duck, carefully maintaining the shape you have created as you do so.