I've decided to frog and start the wrap cardi over in the smaller size. The fabric seems to be very stretchy in this yarn and I think it will also grow, due to the alpaca content. I consulted with my friend, Natalie, over the phone this evening, and she comes to the same concensus. She has made a hat using the Ultra Alpaca, so I bow to her experience, as well. So, if it doesn't come out well, I don't have only myself to blame. Makes me feel better. Heh.
I would show you a picture of my meager progress, but my camera batteries died. It is just as well. I only have a bit more than an inch done from the neck, down. This yarn is so soft and pretty!