It seems that I was rather unrealistic in my sewing plans. I thought that it would be no problem to finish up my muslin and make two pairs of pants and a shirt before going off to Knoxville for the Christmas holiday. At this point this looks completely unlikely. I can recognize however that planning my re-entrance into sewing during the holidays was perhaps a bit ambitious. At least I am making progress, even if slow progress.
The second shirt muslin has been dismantled and altered and new pattern pieces have been created.
I started with the back pieces. First I removed 3/4 inch at the center back, below the bra line but above the waist, tapering to nothing at the side seams. I did not document this as it is a pretty standard alteration. (click on all photos to enlarge)
The next step was to redraw the seam lines. Here you can see the right back, still stitched together but with the new seam lines drawn in red. If you look closely at the drawing, you can see that the original seam where the side back met the center back is to the left of the new red seam line on the upper piece, and to the right of it on the lower piece. The new seam splits the difference between the two.
The next photo shows the same alterations made to the left back piece.
Looking at the entire back laid out flat, with the seam lines marked, suddenly it all made sense to me. Of course these are not the final pieces, and there will be no slashing of the fabric. See how there will be more room in the finished back on the right, room to accommodate the full shoulder blade on the right. The left side will be smaller, and more closely shaped. This will fit more closely over the hollow on that side, where no shoulder blade juts out and where often on purchased clothes there is a large fold of fabric.
Suddenly it all makes sense. Rather than patching a pattern to fit, we have transformed this pattern into something that is designed to fit.
Here are the back pieces, cut apart, seam with all seam lines traced. You can see how the new seams differ from the previous draft.
First the back:
Then the front:
The new patterns have all been created from these pieces and I am ready to cut the third muslin and check the fit.