So, the best I can describe it is... it fits fine across the apex and across my shoulders (when my arms hang down which they aren't in these pix as I'm awkwardly trying to take photos in a mirror) but it's clearly far too broad across the expanse of chest from apex to collarbones (call it the "slope" if you like). So it's not just a matter of simply slicing something off the front panel at the side seams
Click on pic or link to embiggen on all images.
General front view. I know, it's too pointy at the bosom, but that's easily fixed, at least - I'll smooth those lines out on the next draft.
Trying to better show the issue
Reaching forward with my oh-so-toned arms, the problem becomes particularly apparent
Grabbing the gap
This is the pattern I worked out from my basic bodice sloper. It's entirely possible I've done something fundamentally WRONG right here. Enlightenment appreciated!