Awesome video! Was really cool hearing about the story behind the dress and how it pertained to the counterculture movement of the 60’s! Can’t wait to see some of the cool projects you have for us this summer!
There isn't a hard and fast rule that you can't ever set sleeves in flat, but it's generally not recommended for a few reasons. The book you read was before spandex was used as prevalently as it is today. Fit issues: Sleeves with a high curve (more fitted) or with a lot of ease (extra fabric) can be tricky to sew in flat. The armhole and sleeve cap may not match up smoothly, leading to puckers or a sleeve that sticks out instead of conforming to the body. Comfort: Setting sleeves in creates a curved seam under the arm, which allows for more freedom of movement. Flat-sewn sleeves can feel restrictive and uncomfortable. Mostly a truth for wovens like dress shirts. Aesthetics: For woven fabrics (like cotton or linen), a flat-sewn sleeve can sometimes look a bit flat itself, since it doesn't drape as nicely. However, there are some situations where setting in sleeves flat might be okay: Knit fabrics: Knits are naturally more stretchy, so easing the sleeve cap in is often less critical. Simple sleeve designs: Sleeves with a low curve and minimal ease can work well sewn flat. Personal preference: Some sewers find flat-setting easier, especially for beginners.