Whoosh. Well, it wasn't difficult.
I usually flat fell my seams to finish them but I didn't want to do that on the light weight silk, so I thought I would use a French seam finish. I did that on the shoulders but zigzagged around the armholes. Then, I was going to French seam the underarm/side seams when I realized that wouldn't work with having vents on the sides. Instead, I sewed a "normal" right-sides-together seam and then ironed the seam allowance under, thus also making the vent edge finished.
It was at this point that I decided to re-examine my sewing machine for why it was breaking threads. I have a follower who also works where I shop for groceries and we had a nice long talk this week, about threads breaking and people who fix sewing machines. She said something like, "of course, you have checked the throat plate for snags" and I said "of course". But when I was sitting there, this afternoon, staring at my machine, I realized that I had not looked at the throat plate (the plate with the lines on it for 5/8 seam allowances, where the needle goes through the hole into the bobbin area). So I took it out and looked at it and sure enough! There were tiny metal snags where needles have broken over the years. Well. I thought that the sewing machine guy might have said something to me, especially as when I took the machine in, I said "it is breaking the top thread". So I got a tiny piece of very fine emery paper for sanding metal and spent 10 minutes buffing the snags. Then I proceeded to sew rapidly, using straight and zigzag stitches and the thread didn't break once! I did not allow myself to feel elated yet. Then I made six buttonholes and the thread broke twice! Grr. I am going to sand the heck out of the throat plate again and make sure there is nothing snaggy on it and then start a new project and see what happens. I suppose I could also buy a new one.
Anyway, here it is, a tunic length shirt with 3/4 sleeves. It fits and I am happy with the way it turned out. I'll want to wear it once to be sure but I think I have found the pattern for my gold silk. Now, for the sand paper...