Based on some internet perusing to see how others fared with the pattern, I knew I would have to make a few adjustments, as well as figuring out how the twill fabric would work. I lowered the waistline by 2 or 3 inches (the line drawing is deceptive, it's actually quite a bit higher in the pattern itself), and I moved the bodice seams in towards the center 1" each. The bodice still wasn't fitting quite right over the bust, so I took in the top angled bit of the seam some more, which made the neckline all wacky, and I lowered it to fix it. I knew the sleeves would be problematic with the twill, so I cut them back to be tank top straps.
The bust fit is still mushy looking, which I think was actually made worse by the fact I lengthened the top. The pattern is intended to be a looser-fitting top without a zipper, and I think tightening it up and adding a zipper in the side would have fixed that up.
More looseness in the back, which again would be fixed up by adding a zipper and either slimming it up or moving the waist seam back up.
All in all, I'm not super happy with the fit, but I knew it was a bit of a crap shoot going into it. It may end up in my goodwill pile, but it was a fun experiment.