First I decided that I needed to size down my overall size for the jacket. I'm overweight and busty - but I'm also only 5'2". I don't need the jacket as a whole scaled up - I just need room in certain spots. Based on my waist measurement, I'm a size 10 in Gertie-land. So I traced the pattern - in the places that didn't need changes - as a size 10.
Then I took my fitting sloper (it's tissue paper so it's a bit hard to see) and transferred the curves and proportions to the pattern pieces. This is the whole point of having a sloper - being able to use your work elsewhere, and not having to cry and rip and cry and rip every time you sew something new.
Nailed it. :D The upper arm could use a squink more room, the lower arm could use a squink less - and I might give myself a tad more in the center front to play with. But we are in a *very* happy place, and I feel totally ready to cut into my (inexpensive) fashion fabric.
Note on the negative reviews.... I read that the jacket wasn't drafted well. From what Gertie was saying on the video (everyone is watching the video before doing the real work, right? Just like you read the printed instructions first?) she drafted the jacket based on her own proportions. That means you look at Gertie and you have a fair idea of what you're going to have to work with. I haven't done the lining yet (obviously) so I'll report back when I do. So far, so good. I like how this jacket looks, very much, and the fitting changes are far less radical than from a Big Four pattern.
So far, so great. :)