I think I have enough unraveled yarn to knit Jack a vest, but Jack is larger than I am, so I'm not absolutely sure. I decided to knit the vest from top to bottom. If I have to add in other yarn, it will look better at the bottom of the garment rather than the top. I'm going to do the main body of the garment in the round, so I don't have to guess on side one whether I have enough yarn for side two. Right, those decisions made, I knitted a swatch and then did a lot of scribbling and calculations and wrote myself a pattern:
I'm using my favourite mistake rib, which is simply knit two, purl two rib worked on an odd number of stitches. I'm using a circular needle for the top parts, even though they're worked back and forth, just so I use the same needles throughout.