Well, duh. No wonder I couldn't make the math work. 8-ply is a DK, not a worsted.
But the girls at the Sheep were applying some light peer pressure today re: my Olympic project. It's true that that this is about finding a proper challenge -- and my challenge is lace knitting. So a lace shawl seems like it would be the thing to do. We chose the Wool Peddler's Shawl in Folk Shawls, and I tried very hard to choose some yarn, but I couldn't find enough in a colour I liked that wouldn't kill me (that is, not black).
So I will continue to look around and think.
The Wool Peddler has a fair bit of garter stitch to get me moving. Since this is my first lace project (Clapotis doesn't count), I think I need to keep it pretty simple. Although I do like some of the full-lace ones in the book, I might die.