Okay, I'm feeling a bit more like trying it out myself. Seeing Matt's in the thread I linked above, I recalled that I had what I thought was a wool long-sleeved Fair Isle that I hadn't worn for years but never threw out. I went looking and found it, still in "like new" condition. It's from Eddie Bauer, sometime in the '80s I think. Looking at the inside, it does appear to be a proper Fair Isle knit, and the label says it's Shetland wool. It's too warm here to try it out this week, but I think this one would go particularly well with the Douglas Weathered kilt Matt made for me: