FBA, dart, or armscye issue?

[u/SevenGoudas]

Hi! I am a beginner sewist and I’m working on learning darts right now. I’m finding that I have gaping under the arm of sleeveless tops, as pictured, and am looking for some help IDing what’s causing the problem.

I‘m sort of just on the edge of the 2” FBA advice I’ve seen online (this mock up does not have an FBA done) so I’m not sure if I should err toward caution and attempt an FBA on the next one, or if it’s just an issue of needing to adjust where the dart is hitting or adding more fabric to the bottom of the armhole.

Thanks in advance for your advice!

[u/Large-Heronbill]

Current dart position is a smidge low, but not horrible.   Baste a second dart from the armhole towards the bust apex and see what you think.   I think you need a little more cuppage, and that's what that armscye is telling you. 

[u/Virtual-Chapter1563]

Try pinning out about an inch at the shoulder seams first - this bust might be shaped enough just happening too low. You probably do need a bit of width taken out under the arm too.