Because I just bet I'm gonna wind up knitting this sweater on ones and zeros (2.25mm and 2mm).
The lower part of the swatch is knit on size twos (2.75mm). About halfway up the color part, I shifted over to size ones to see how it looked, and as soon as I changed needles I knew I had the right needle size. The yarn holds together better, doesn't slide around, doing the colorwork is easier, it looks better, and worst of all, THE GAUGE IS SPOT-ON. I wanted nine stitches per inch. I get that with size one needles.
Since my gauge is always tighter doing stranded color than it is doing regular stockinette, that means the plain bits will have to be done on zeros.
Of course, this is all subject to change once the swatch hits water. Coned yarns can do seriously crazy things when they hit water. But I doubt it's going to make the gauge SMALLER (never has in my experience, unless you're felting it), which is what I need.
I'm telling myself, how much worse can it be? I was thinking it would be size ones, and it's size zeros. No big deal. I'm already insane.