Next up!

So After finishing the Roundabout Tank I started a few other projects. I brought the book with me one weekend when I went to visit my parents in Rhode Island and my brother found it. He's been asking me to do knit him a sweater for quite some time, but we could never decide on the right pattern. He found this:

And of course this is the sweater he wants me to knit him before Christmas!. He claims to have an allergy to wool, and so I'm thinking of knitting this out of cotton or a cotton/wool blend that is much more cottony than wooly. He's picked out, from Knit Picks, Main Line in Blueberry. I've never used the yarn that is required in the pattern (Harrisville Highland Style) and know that the weight seems to be about the same, but was still wondering how you folks thought this would substitute.