The first time I made this pattern the armholes pulled forward and gaped, and the neckline waved, gaped, wouldn't lie flat against my chest and was completely revealing.
It's Butterick pattern 3385 View C and I cut a size 8. My bust measurement would have me at a 14 going from the pattern measurements, or a 12 going from my high bust measurement, but the finished garment waist measurement for the size 8 was 30" which gives me 2" of ease for my 28" waist. I always have to buy for my waist because even the high bust measurement isn't accurate when selecting a pattern (for me). So naturally when I first made it, it fit my waist perfectly and my chest terribly! I followed the instructions on that site and spread the pattern by 2cm for the C cup, converted the side dart to ease (which I wont do next time, a dart will me much neater), and the width was gathered under the bust. When I put it on it was magic!! It fit across my chest perfectly! I am so impressed with this, and am going to alter all my patterns now!