What I've decided to do with the red yarn is a henley version of Ysolda's 'Cria'. (link later, sorry)
I've done a very thorough swatch. And washed it and dried it and then "weighted" it for a few hours, as instructed. And the gauge is ridiculous. Bigger than the label said I'd get with needles two sizes larger. Row gauge ratio to stitch gauge unexpected, too.
I've done a lot of math. Will cast on and hope. At least it's top down. True disaster should be spottable fairly early.