Looking for Advice on Larger Sizes...

Hi All! Thanks for letting me join the knitalong...

I have my yarn (Black Water Abbey in rust) and my swatch (right on with stitch gauge, but a little off on row gauge) -- but am having trouble deciding on a size.

In particular, I'm worried about armhole depth... If I look at the schematic, the armhole depth for the largest size is 14.75". Even though the largest size looks like it would fit me by the bust and upper arm circumference, an armhole depth of 14.75" would put the armholes halfway down my back. I measured a bunch of my other cardigans and jackets and their armhole depths were more like 12" - 12.5". (Which would correspond to the middle size.) In other places on a sweater 2" isn't that big a deal, but I'm worried that it'll just look too sloppy if the underarms are too low.

Has anyone made one of the two larger sizes? Do the underarms end up in the right place? Am I misreading the schematic? Does part of that measurement end up in a collar or something?

I'm anxious to cast on, but am so enamored by this sweater that I really want it to fit!
Thanks.