So the vest has been felted, and it fits pretty well. I'm thinking I'll do a little hand-felting around the shoulders, or maybe throw it in for a little longer, just to tighten it up a bit. It felted very fast. I was felting it in 5 minute intervals, and it was nearly to its finished dimensions after only 15 minutes, and was done after another 3!
All that is left to do on it is replace the yellow cotton with the beige wool, and iron it to smooth the felt down a bit. I'm very happy with this vest, and I think it will serve me well. If I decide to make another one, though, I will be using a Knitting Machine. They're not too expensive, and you can often get them for 40% off at AC Moore or Joanne's.