I think I've just had an "ah ha!" moment and I'm hoping that any sweater knitters who happen to stop by can confirm.
I don't have a whole lot of luck with sweater sizing. I'm always just a bit off. I knit swatches and manage to get and keep gauge. I wear a size 36 bra and usually knit the size closest to 36. The lightbulb moment came here....we're supposed to measure around the fullest part of the bust, right? Because I wear a 36D - so the fullest part is actually 41". So when I'm knitting the pattern somewhere in the 36" - 38" range, I'm dooming myself to failure, aren't I?
Shoot! And wow.