For the longest while I've wanted a simple sleeveless shell that was easy to make and easy to wear. No buttons, no zippers, just over the head, but I've always had this problem with the front armhole gaping. I know, I know, I've seen the old dart into the armscye trick and that seemed, well, like a cop-out to me. I know any other sewer would see that dart and think "Oh dear, I guess she just gave up!" So after much drafting and muslining I have finally eradicated gaping. For now anyway. And I have 5 blouses and 2 dresses and more on the way.
I started out with an old pattern I already had-Simplicity 8523.
I picked the pattern size based on the upper chest measurement and then did a FBA adding an additional 3 inches in the bust. Maybe in the past my problem was starting with too big a size? I'm glad this has only taken me 30 years to figure out.
Then I rotated the dart to under the bust & added a seam under the bust.
I used the back pattern piece, but added a center seam for more shaping.
Finally, I eliminated the facings and finished the opening with bias tape. I can put this top together in about 2 hours. I love bias tape! I have one more cut out for now, but would maybe like to make more fitted one with a side zipper. And I have just the fabric, too.