I pulled out sleeve pattern pieces, and front and back pieces from different patterns, and layered them to see how different they were from each other, and maybe try to figure out why some shirts wouldn't allow me to stretch my arms out in front of me.
I didn't find anything! The sleeves were practically identical in the shirts that didn't work, compared to the shirts that did work. Same with the fronts and backs. I went to the closet and tried on the shirts that don't work (why do I still have them hanging there, you ask? I ask that too.) The only thing I can think of is that all the shirts that work have a little Lycra in the fabric. And I think it is the width of the back that makes the difference, not the type of sleeve. In other words, my problem is that the back isn't wide enough, which means I am too big for the pattern. I can stand to lose 10 to 15 pounds and there it is - a whole pattern size. sigh.
I also looked at the sleeveless shirts I had made (and never worn) from the Vogue pattern 2634 and then I looked at the pattern and slapped myself up-side the head. It was a size 10, even smaller than the 12 with which I was having issues.
I decided to go with the McCall's 5630 "perfect fit" pattern and start to modify it. I pulled out the pattern pieces and discovered that I had already made this pattern!
Again, I used cotton with a little Lycra in it. I wasn't all that happy with how big the collar was but the shirt was a pretty good fit otherwise.
So what I did was cut the collar back at the points, so it would be a bit smaller. I've done this before with good results.
I had it in mind that I would use some plain cream coloured fabric I had, but in the process of looking for it (I have boxes and boxes of fabric), I found some nice striped cotton (no Lycra!). It is a little thicker than the silk but I think it will be okay for a template. My plan is to make the body straight, so it is more like a tunic than a shaped shirt. It won't be as long or as baggy as a tunic, but I want the stripes to be straight, all the way up and down.
When I cut out the front and back pieces, I cut as straight down the stripes in the fabric as I could, eliminating the curve in at the waist. I will still put in the bust darts but I won't put in the vertical front and back shaping darts. It will be interesting to see how boxy and bulky the shirt looks with no vertical shaping.