The good news: I've managed to scrape together a couple of hours over the last couple of days to cut out and baste together my test "muslin" for the jeans.
The bad news: the fitting is going to be way more complicated than I thought! I'm going to assume it's probably my own fault for tracing the pattern the way I did-- for lack of good paper to use with the tracing wheel (the only option at Joann's is terrible), I had to approximate with a wash-off fabric marker. But somehow, not only were the jeans too small all around my thighs, the rise sits lower to the point where my cut line is probably where my seam should be, and they gap in the back. And I still don't know how to draft the waistband. So no pictures of the progress so far, because it is not going to look good. Or safe for public consumption, for that matter.
On the plus side, the wrinkles in the front that I had so much trouble with on my last jeans-fitting attempt weren't that bad, and when I have a waistband to hold the top up, that problem just might be solved. (I won't know for sure until I have a waistband, because I also need to see what happens when I try to sit down.)
So I've already abandoned the idea of trying to reuse this particular piece of fabric-- I'm going to have to do a lot more marking up than I thought, and possibly re-cut the yoke entirely. If it's bad enough, I may have to just suck it up and make another one with regular muslin, because I don't want to blow another $18 on twill that I'm just going to destroy. I'm a bit bummed that I blew this one. But I guess it's better than ruining the more expensive denim, right?
So far, I've let out both the inner and outer leg seams about 1/8" (for a total of 1/2" per leg) down to about the knee, and that made a big difference already. At least I can put them on without breaking the zipper now! I think I still might let it out a little bit more, because it's still a bit tighter around the thighs than I want to do with non-stretch fabric. I can't continue on it any more tonight, because I have some chores around the house that need to get done, but at least I have something started. And if I can get this figured out, it'll be a great learning experience!
I may need to look into getting some of that better tracing paper from some website or other....I'm already cringing at the thought of transferring this back to the pattern!