Well I'm almost done, been working on it all day. I thought ahead and made a template out of ripstop so that I didn't have to repeat measurements, then I cut out the shell and insultex from the template.
I'm doing things a little differently than the KAQ way. I'm hemming the IX and the shell, then attaching the draw cord channels to the shell, then sewing the IX across the shell and channels so that the channels have two lines of stitching, IX will have one (I'll double up on it later if it doesn't look reliable) and all the edges will be hemmed.
Here's a shot of the shell, IX beneath it, and the IX scraps on top. I'm going to sew those together into a rectangular pad which I'll orient where my torso will be for a little extra insulation.