Oh got it! Yeah, you don’t want a gaping neckline. so if your pattern choice based on the upper bust measurement, you’ll want to make a muslin. If the neckline fits and the bust doesn’t then you can use the pivot and slide to fix the bustline, this shouldn’t effect the neckline. OR you can choose your pattern based on your full bustline measurement and then make alterations to the neckline and fix the gape. Again, you’d need to make a muslin, pinch and measure the gape to know how much to take out. There’s actually a good demo on pattern alteration to fix a gape here: https://katrinakaycreations.com/make-gaping-neckline-pattern-adjustment/ You might find, altering a pattern to fix the gape might be easier than fixing the bustline. It’s really up to you.